<?xml version="1.0" encoding="US-ASCII"?>
<!--XBRL Document Created with Wdesk from Workiva-->
<!-- -->
<link:linkbase xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <link:roleRef roleURI="http://miacquisitions.com/role/AccountsPayableAndAccruedExpenses" xlink:href="prth-20200630.xsd#AccountsPayableAndAccruedExpenses" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/AccountsPayableAndAccruedExpensesScheduleOfAccountsPayableAndAccruedExpensesDetails" xlink:href="prth-20200630.xsd#AccountsPayableAndAccruedExpensesScheduleOfAccountsPayableAndAccruedExpensesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/AccountsPayableAndAccruedExpensesTables" xlink:href="prth-20200630.xsd#AccountsPayableAndAccruedExpensesTables" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/BasisOfPresentationAndSignificantAccountingPolicies" xlink:href="prth-20200630.xsd#BasisOfPresentationAndSignificantAccountingPolicies" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/BasisOfPresentationAndSignificantAccountingPoliciesPolicies" xlink:href="prth-20200630.xsd#BasisOfPresentationAndSignificantAccountingPoliciesPolicies" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/CommitmentsAndContingencies" xlink:href="prth-20200630.xsd#CommitmentsAndContingencies" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/CommitmentsAndContingenciesNarrativeDetails" xlink:href="prth-20200630.xsd#CommitmentsAndContingenciesNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/CondensedConsolidatedBalanceSheets" xlink:href="prth-20200630.xsd#CondensedConsolidatedBalanceSheets" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/CondensedConsolidatedBalanceSheetsParenthetical" xlink:href="prth-20200630.xsd#CondensedConsolidatedBalanceSheetsParenthetical" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/CondensedConsolidatedStatementsOfCashFlows" xlink:href="prth-20200630.xsd#CondensedConsolidatedStatementsOfCashFlows" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/CondensedConsolidatedStatementsOfOperations" xlink:href="prth-20200630.xsd#CondensedConsolidatedStatementsOfOperations" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/Cover" xlink:href="prth-20200630.xsd#Cover" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/DebtObligations" xlink:href="prth-20200630.xsd#DebtObligations" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/DebtObligationsEffectiveInterestRatesDetails" xlink:href="prth-20200630.xsd#DebtObligationsEffectiveInterestRatesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/DebtObligationsNarrativeDetails" xlink:href="prth-20200630.xsd#DebtObligationsNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/DebtObligationsRollingMaturitiesOfLongTermDebtDetails" xlink:href="prth-20200630.xsd#DebtObligationsRollingMaturitiesOfLongTermDebtDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/DebtObligationsScheduleOfLongTermDebtDetails" xlink:href="prth-20200630.xsd#DebtObligationsScheduleOfLongTermDebtDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/DebtObligationsTables" xlink:href="prth-20200630.xsd#DebtObligationsTables" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/FairValue" xlink:href="prth-20200630.xsd#FairValue" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/FairValueNarrativeDetails" xlink:href="prth-20200630.xsd#FairValueNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/GoodwillAndIntangibleAssets" xlink:href="prth-20200630.xsd#GoodwillAndIntangibleAssets" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/GoodwillAndIntangibleAssetsGoodwillAllocationDetails" xlink:href="prth-20200630.xsd#GoodwillAndIntangibleAssetsGoodwillAllocationDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/GoodwillAndIntangibleAssetsIntangibleAssetsDetails" xlink:href="prth-20200630.xsd#GoodwillAndIntangibleAssetsIntangibleAssetsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/GoodwillAndIntangibleAssetsNarrativeDetails" xlink:href="prth-20200630.xsd#GoodwillAndIntangibleAssetsNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/GoodwillAndIntangibleAssetsTables" xlink:href="prth-20200630.xsd#GoodwillAndIntangibleAssetsTables" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/IncomeTaxes" xlink:href="prth-20200630.xsd#IncomeTaxes" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/IncomeTaxesNarrativeDetails" xlink:href="prth-20200630.xsd#IncomeTaxesNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/IncomeTaxesScheduleOfIncomeTaxBenefitProvisionDetails" xlink:href="prth-20200630.xsd#IncomeTaxesScheduleOfIncomeTaxBenefitProvisionDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/IncomeTaxesTables" xlink:href="prth-20200630.xsd#IncomeTaxesTables" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/LossPerCommonShare" xlink:href="prth-20200630.xsd#LossPerCommonShare" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/LossPerCommonShareScheduleOfAntidilutiveSecuritiesDetails" xlink:href="prth-20200630.xsd#LossPerCommonShareScheduleOfAntidilutiveSecuritiesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/LossPerCommonShareScheduleOfEarningsPerShareDetails" xlink:href="prth-20200630.xsd#LossPerCommonShareScheduleOfEarningsPerShareDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/LossPerCommonShareTables" xlink:href="prth-20200630.xsd#LossPerCommonShareTables" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/NonControllingInterests" xlink:href="prth-20200630.xsd#NonControllingInterests" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/NonControllingInterestsYapstoneDetails" xlink:href="prth-20200630.xsd#NonControllingInterestsYapstoneDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/PropertyEquipmentAndSoftware" xlink:href="prth-20200630.xsd#PropertyEquipmentAndSoftware" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/PropertyEquipmentAndSoftwareNarrativeAndScheduleOfPropertyEquipmentAndSoftwareDetails" xlink:href="prth-20200630.xsd#PropertyEquipmentAndSoftwareNarrativeAndScheduleOfPropertyEquipmentAndSoftwareDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/PropertyEquipmentAndSoftwareTables" xlink:href="prth-20200630.xsd#PropertyEquipmentAndSoftwareTables" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/ReconciliationOfStockholdersDeficitAndNonControllingInterest" xlink:href="prth-20200630.xsd#ReconciliationOfStockholdersDeficitAndNonControllingInterest" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/ReconciliationOfStockholdersDeficitAndNonControllingInterestEquityReconciliationDetails" xlink:href="prth-20200630.xsd#ReconciliationOfStockholdersDeficitAndNonControllingInterestEquityReconciliationDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/ReconciliationOfStockholdersDeficitAndNonControllingInterestNarrativeDetails" xlink:href="prth-20200630.xsd#ReconciliationOfStockholdersDeficitAndNonControllingInterestNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/ReconciliationOfStockholdersDeficitAndNonControllingInterestTables" xlink:href="prth-20200630.xsd#ReconciliationOfStockholdersDeficitAndNonControllingInterestTables" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/RelatedPartyTransactions" xlink:href="prth-20200630.xsd#RelatedPartyTransactions" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/RelatedPartyTransactionsNarrativeDetails" xlink:href="prth-20200630.xsd#RelatedPartyTransactionsNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/Revenues" xlink:href="prth-20200630.xsd#Revenues" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/RevenuesBalanceSheetInformationDetails" xlink:href="prth-20200630.xsd#RevenuesBalanceSheetInformationDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/RevenuesDisaggregationOfRevenueDetails" xlink:href="prth-20200630.xsd#RevenuesDisaggregationOfRevenueDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/RevenuesNarrativeDetails" xlink:href="prth-20200630.xsd#RevenuesNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/RevenuesTables" xlink:href="prth-20200630.xsd#RevenuesTables" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/SegmentInformation" xlink:href="prth-20200630.xsd#SegmentInformation" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/SegmentInformationNarrativeDetails" xlink:href="prth-20200630.xsd#SegmentInformationNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/SegmentInformationScheduleOfReconciliationOfTotalOperatingIncomeDetails" xlink:href="prth-20200630.xsd#SegmentInformationScheduleOfReconciliationOfTotalOperatingIncomeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/SegmentInformationScheduleOfSegmentReportingInformationBySegmentDetails" xlink:href="prth-20200630.xsd#SegmentInformationScheduleOfSegmentReportingInformationBySegmentDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/SegmentInformationTables" xlink:href="prth-20200630.xsd#SegmentInformationTables" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/SettlementAssetsAndObligations" xlink:href="prth-20200630.xsd#SettlementAssetsAndObligations" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/SettlementAssetsAndObligationsDetails" xlink:href="prth-20200630.xsd#SettlementAssetsAndObligationsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/SettlementAssetsAndObligationsTables" xlink:href="prth-20200630.xsd#SettlementAssetsAndObligationsTables" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/StockBasedCompensationPlans" xlink:href="prth-20200630.xsd#StockBasedCompensationPlans" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/StockBasedCompensationPlansSummaryOfEquityBasedCompensationExpenseDetails" xlink:href="prth-20200630.xsd#StockBasedCompensationPlansSummaryOfEquityBasedCompensationExpenseDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://miacquisitions.com/role/StockBasedCompensationPlansTables" xlink:href="prth-20200630.xsd#StockBasedCompensationPlansTables" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension" xlink:type="simple" />
  <link:definitionLink xlink:role="http://miacquisitions.com/role/AccountsPayableAndAccruedExpenses" xlink:type="extended" />
  <link:definitionLink xlink:role="http://miacquisitions.com/role/AccountsPayableAndAccruedExpensesScheduleOfAccountsPayableAndAccruedExpensesDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://miacquisitions.com/role/AccountsPayableAndAccruedExpensesTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://miacquisitions.com/role/BasisOfPresentationAndSignificantAccountingPolicies" xlink:type="extended" />
  <link:definitionLink xlink:role="http://miacquisitions.com/role/BasisOfPresentationAndSignificantAccountingPoliciesPolicies" xlink:type="extended" />
  <link:definitionLink xlink:role="http://miacquisitions.com/role/CommitmentsAndContingencies" xlink:type="extended" />
  <link:definitionLink xlink:role="http://miacquisitions.com/role/CommitmentsAndContingenciesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="prth-20200630.xsd#prth_ScheduleofAssetAcquisitionLineItems" xlink:label="loc_prth_ScheduleofAssetAcquisitionLineItems_D369186481BA8C0CFDEDD99ECD082C8B" xlink:type="locator" />
    <link:loc xlink:href="prth-20200630.xsd#prth_ScheduleofAssetAcquisitionTable" xlink:label="loc_prth_ScheduleofAssetAcquisitionTable_4E4AC63C5E1C2EF27B69D99ECCF0D7D0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_prth_ScheduleofAssetAcquisitionLineItems_D369186481BA8C0CFDEDD99ECD082C8B" xlink:to="loc_prth_ScheduleofAssetAcquisitionTable_4E4AC63C5E1C2EF27B69D99ECCF0D7D0" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_DD98A25C0968030E45C0D99ECCF112EC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_prth_ScheduleofAssetAcquisitionTable_4E4AC63C5E1C2EF27B69D99ECCF0D7D0" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_DD98A25C0968030E45C0D99ECCF112EC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_470BBD7B8A4D9C513142D99ECCF13049_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_DD98A25C0968030E45C0D99ECCF112EC" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_470BBD7B8A4D9C513142D99ECCF13049_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_470BBD7B8A4D9C513142D99ECCF13049" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_DD98A25C0968030E45C0D99ECCF112EC" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_470BBD7B8A4D9C513142D99ECCF13049" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ServiceAgreementsMember" xlink:label="loc_us-gaap_ServiceAgreementsMember_DE09327F0DC7F0383D5ED99ECCF427B6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_470BBD7B8A4D9C513142D99ECCF13049" xlink:to="loc_us-gaap_ServiceAgreementsMember_DE09327F0DC7F0383D5ED99ECCF427B6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CreditFacilityAxis" xlink:label="loc_us-gaap_CreditFacilityAxis_B40B1A9FF05262F11BA6D99ECCF5136A" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_prth_ScheduleofAssetAcquisitionTable_4E4AC63C5E1C2EF27B69D99ECCF0D7D0" xlink:to="loc_us-gaap_CreditFacilityAxis_B40B1A9FF05262F11BA6D99ECCF5136A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CreditFacilityDomain" xlink:label="loc_us-gaap_CreditFacilityDomain_3499A4D26D394B70DA33D99ECCF7291A_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_B40B1A9FF05262F11BA6D99ECCF5136A" xlink:to="loc_us-gaap_CreditFacilityDomain_3499A4D26D394B70DA33D99ECCF7291A_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CreditFacilityDomain" xlink:label="loc_us-gaap_CreditFacilityDomain_3499A4D26D394B70DA33D99ECCF7291A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_B40B1A9FF05262F11BA6D99ECCF5136A" xlink:to="loc_us-gaap_CreditFacilityDomain_3499A4D26D394B70DA33D99ECCF7291A" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_TermLoanMember" xlink:label="loc_prth_TermLoanMember_78F75D75A2942C1DF58FD99ECCF9D8F8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_3499A4D26D394B70DA33D99ECCF7291A" xlink:to="loc_prth_TermLoanMember_78F75D75A2942C1DF58FD99ECCF9D8F8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevolvingCreditFacilityMember" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_C82560786B6B00BDC51AD99ECCF90C1D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_3499A4D26D394B70DA33D99ECCF7291A" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_C82560786B6B00BDC51AD99ECCF90C1D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditFacilityAxis" xlink:label="loc_us-gaap_LineOfCreditFacilityAxis_2817D24134AE2BA426FAD99ECCF9136E" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_prth_ScheduleofAssetAcquisitionTable_4E4AC63C5E1C2EF27B69D99ECCF0D7D0" xlink:to="loc_us-gaap_LineOfCreditFacilityAxis_2817D24134AE2BA426FAD99ECCF9136E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditFacilityLenderDomain" xlink:label="loc_us-gaap_LineOfCreditFacilityLenderDomain_FECD415A1ACF5DA5FFA6D99ECCFB584B_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LineOfCreditFacilityAxis_2817D24134AE2BA426FAD99ECCF9136E" xlink:to="loc_us-gaap_LineOfCreditFacilityLenderDomain_FECD415A1ACF5DA5FFA6D99ECCFB584B_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditFacilityLenderDomain" xlink:label="loc_us-gaap_LineOfCreditFacilityLenderDomain_FECD415A1ACF5DA5FFA6D99ECCFB584B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LineOfCreditFacilityAxis_2817D24134AE2BA426FAD99ECCF9136E" xlink:to="loc_us-gaap_LineOfCreditFacilityLenderDomain_FECD415A1ACF5DA5FFA6D99ECCFB584B" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_SyndicateOfLendersMember" xlink:label="loc_prth_SyndicateOfLendersMember_8A2DE16C58715CB79847D99ECD01C8EF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLenderDomain_FECD415A1ACF5DA5FFA6D99ECCFB584B" xlink:to="loc_prth_SyndicateOfLendersMember_8A2DE16C58715CB79847D99ECD01C8EF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeAxis" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_68C315B0CFCBC0E7A91BD99ECD047415" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_prth_ScheduleofAssetAcquisitionTable_4E4AC63C5E1C2EF27B69D99ECCF0D7D0" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_68C315B0CFCBC0E7A91BD99ECD047415" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_2C5A16999DE987DCAD4BD99ECD06773B_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_68C315B0CFCBC0E7A91BD99ECD047415" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_2C5A16999DE987DCAD4BD99ECD06773B_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_2C5A16999DE987DCAD4BD99ECD06773B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_68C315B0CFCBC0E7A91BD99ECD047415" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_2C5A16999DE987DCAD4BD99ECD06773B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditMember" xlink:label="loc_us-gaap_LineOfCreditMember_E1F4ABB61AFBB3442AC6D99ECD06D340" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_2C5A16999DE987DCAD4BD99ECD06773B" xlink:to="loc_us-gaap_LineOfCreditMember_E1F4ABB61AFBB3442AC6D99ECD06D340" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongTermPurchaseCommitmentAmount" xlink:label="loc_us-gaap_LongTermPurchaseCommitmentAmount_FCE3546245A35445D225D99ECD084616" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_prth_ScheduleofAssetAcquisitionLineItems_D369186481BA8C0CFDEDD99ECD082C8B" xlink:to="loc_us-gaap_LongTermPurchaseCommitmentAmount_FCE3546245A35445D225D99ECD084616" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_NumberofAgreements" xlink:label="loc_prth_NumberofAgreements_73AC4D37E1A554CCC07ED99ECD0A7DB3" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_prth_ScheduleofAssetAcquisitionLineItems_D369186481BA8C0CFDEDD99ECD082C8B" xlink:to="loc_prth_NumberofAgreements_73AC4D37E1A554CCC07ED99ECD0A7DB3" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_ResellerArrangementPeriod" xlink:label="loc_prth_ResellerArrangementPeriod_AEFF8A6048B5FD3CBD6BD99ECD0AAB7F" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_prth_ScheduleofAssetAcquisitionLineItems_D369186481BA8C0CFDEDD99ECD082C8B" xlink:to="loc_prth_ResellerArrangementPeriod_AEFF8A6048B5FD3CBD6BD99ECD0AAB7F" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_AssetAcquisitionContingentConsideration" xlink:label="loc_prth_AssetAcquisitionContingentConsideration_A2E1FEAC9FEC82AB43C6D99ECD0A2D10" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_prth_ScheduleofAssetAcquisitionLineItems_D369186481BA8C0CFDEDD99ECD082C8B" xlink:to="loc_prth_AssetAcquisitionContingentConsideration_A2E1FEAC9FEC82AB43C6D99ECD0A2D10" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_AssetAcquisitionIntangibleAssets" xlink:label="loc_prth_AssetAcquisitionIntangibleAssets_22FDB17BFDD4CF3D763CD99ECD0C7FEA" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_prth_ScheduleofAssetAcquisitionLineItems_D369186481BA8C0CFDEDD99ECD082C8B" xlink:to="loc_prth_AssetAcquisitionIntangibleAssets_22FDB17BFDD4CF3D763CD99ECD0C7FEA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ProceedsFromLinesOfCredit" xlink:label="loc_us-gaap_ProceedsFromLinesOfCredit_08F367D62025423AD464D99ECD0D1948" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_prth_ScheduleofAssetAcquisitionLineItems_D369186481BA8C0CFDEDD99ECD082C8B" xlink:to="loc_us-gaap_ProceedsFromLinesOfCredit_08F367D62025423AD464D99ECD0D1948" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_ContingentCashPaymentsForAssetAcquisitions" xlink:label="loc_prth_ContingentCashPaymentsForAssetAcquisitions_0B09549C37A355FB01F6D99ECD0D49F6" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_prth_ScheduleofAssetAcquisitionLineItems_D369186481BA8C0CFDEDD99ECD082C8B" xlink:to="loc_prth_ContingentCashPaymentsForAssetAcquisitions_0B09549C37A355FB01F6D99ECD0D49F6" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://miacquisitions.com/role/CondensedConsolidatedBalanceSheets" xlink:type="extended" />
  <link:definitionLink xlink:role="http://miacquisitions.com/role/CondensedConsolidatedBalanceSheetsParenthetical" xlink:type="extended" />
  <link:definitionLink xlink:role="http://miacquisitions.com/role/CondensedConsolidatedStatementsOfCashFlows" xlink:type="extended" />
  <link:definitionLink xlink:role="http://miacquisitions.com/role/CondensedConsolidatedStatementsOfOperations" xlink:type="extended" />
  <link:definitionLink xlink:role="http://miacquisitions.com/role/Cover" xlink:type="extended" />
  <link:definitionLink xlink:role="http://miacquisitions.com/role/DebtObligations" xlink:type="extended" />
  <link:definitionLink xlink:role="http://miacquisitions.com/role/DebtObligationsEffectiveInterestRatesDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentLineItems" xlink:label="loc_us-gaap_DebtInstrumentLineItems_929D2DBC7B69309A398BE7EF56769B1F" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentTable" xlink:label="loc_us-gaap_DebtInstrumentTable_C48054C3117E98C8E12DE7EF566D7164" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_929D2DBC7B69309A398BE7EF56769B1F" xlink:to="loc_us-gaap_DebtInstrumentTable_C48054C3117E98C8E12DE7EF566D7164" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CreditFacilityAxis" xlink:label="loc_us-gaap_CreditFacilityAxis_7356EC688338DE3DF59DE7F0781B05C5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_C48054C3117E98C8E12DE7EF566D7164" xlink:to="loc_us-gaap_CreditFacilityAxis_7356EC688338DE3DF59DE7F0781B05C5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CreditFacilityDomain" xlink:label="loc_us-gaap_CreditFacilityDomain_8788C8274F26E89F68ECE7F0781CB781_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_7356EC688338DE3DF59DE7F0781B05C5" xlink:to="loc_us-gaap_CreditFacilityDomain_8788C8274F26E89F68ECE7F0781CB781_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CreditFacilityDomain" xlink:label="loc_us-gaap_CreditFacilityDomain_8788C8274F26E89F68ECE7F0781CB781" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_7356EC688338DE3DF59DE7F0781B05C5" xlink:to="loc_us-gaap_CreditFacilityDomain_8788C8274F26E89F68ECE7F0781CB781" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevolvingCreditFacilityMember" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_66279EE6EA55D8EF7544E7F0789B9F12" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_8788C8274F26E89F68ECE7F0781CB781" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_66279EE6EA55D8EF7544E7F0789B9F12" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditFacilityAxis" xlink:label="loc_us-gaap_LineOfCreditFacilityAxis_0B232B1965476D0992CBE7EFBC836E72" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_C48054C3117E98C8E12DE7EF566D7164" xlink:to="loc_us-gaap_LineOfCreditFacilityAxis_0B232B1965476D0992CBE7EFBC836E72" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditFacilityLenderDomain" xlink:label="loc_us-gaap_LineOfCreditFacilityLenderDomain_D2A06F2A9561F7D38C20E7EFBC8B4189_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LineOfCreditFacilityAxis_0B232B1965476D0992CBE7EFBC836E72" xlink:to="loc_us-gaap_LineOfCreditFacilityLenderDomain_D2A06F2A9561F7D38C20E7EFBC8B4189_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditFacilityLenderDomain" xlink:label="loc_us-gaap_LineOfCreditFacilityLenderDomain_D2A06F2A9561F7D38C20E7EFBC8B4189" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LineOfCreditFacilityAxis_0B232B1965476D0992CBE7EFBC836E72" xlink:to="loc_us-gaap_LineOfCreditFacilityLenderDomain_D2A06F2A9561F7D38C20E7EFBC8B4189" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_SyndicateOfLendersMember" xlink:label="loc_prth_SyndicateOfLendersMember_48C3ED766E1DC6121DA0E7EFBD1D0684" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLenderDomain_D2A06F2A9561F7D38C20E7EFBC8B4189" xlink:to="loc_prth_SyndicateOfLendersMember_48C3ED766E1DC6121DA0E7EFBD1D0684" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_GoldmanSachsSpecialtyLendingGroupMember" xlink:label="loc_prth_GoldmanSachsSpecialtyLendingGroupMember_2D349815534DAAF7388CE7F26C25343F" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLenderDomain_D2A06F2A9561F7D38C20E7EFBC8B4189" xlink:to="loc_prth_GoldmanSachsSpecialtyLendingGroupMember_2D349815534DAAF7388CE7F26C25343F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeAxis" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_DB3FBE9714BDBA2E7DCCE7EF566EAAE8" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_C48054C3117E98C8E12DE7EF566D7164" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_DB3FBE9714BDBA2E7DCCE7EF566EAAE8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_EFC03F61A2455CBA2732E7EF566FD17E_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_DB3FBE9714BDBA2E7DCCE7EF566EAAE8" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_EFC03F61A2455CBA2732E7EF566FD17E_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_EFC03F61A2455CBA2732E7EF566FD17E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_DB3FBE9714BDBA2E7DCCE7EF566EAAE8" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_EFC03F61A2455CBA2732E7EF566FD17E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditMember" xlink:label="loc_us-gaap_LineOfCreditMember_EDFE3FEA7F3C2EEAB6E8E7F0775B86D7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_EFC03F61A2455CBA2732E7EF566FD17E" xlink:to="loc_us-gaap_LineOfCreditMember_EDFE3FEA7F3C2EEAB6E8E7F0775B86D7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditFacilityInterestRateDuringPeriod" xlink:label="loc_us-gaap_LineOfCreditFacilityInterestRateDuringPeriod_1C2367A4C39D88756FA3E7F184DE8D01" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_929D2DBC7B69309A398BE7EF56769B1F" xlink:to="loc_us-gaap_LineOfCreditFacilityInterestRateDuringPeriod_1C2367A4C39D88756FA3E7F184DE8D01" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://miacquisitions.com/role/DebtObligationsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentLineItems" xlink:label="loc_us-gaap_DebtInstrumentLineItems_A5B3A0FD41A00FB8A0DFE7E9788F1A78" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentTable" xlink:label="loc_us-gaap_DebtInstrumentTable_A8084CC9E34BAFD13174E7E978879A52" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_A5B3A0FD41A00FB8A0DFE7E9788F1A78" xlink:to="loc_us-gaap_DebtInstrumentTable_A8084CC9E34BAFD13174E7E978879A52" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventTypeAxis" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_A4231F268BB3D2E177B9E7E978872F8A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_A8084CC9E34BAFD13174E7E978879A52" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_A4231F268BB3D2E177B9E7E978872F8A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_B4420EBD4066C98075C0E7E97888F2D2_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_A4231F268BB3D2E177B9E7E978872F8A" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_B4420EBD4066C98075C0E7E97888F2D2_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_B4420EBD4066C98075C0E7E97888F2D2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_A4231F268BB3D2E177B9E7E978872F8A" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_B4420EBD4066C98075C0E7E97888F2D2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventMember" xlink:label="loc_us-gaap_SubsequentEventMember_E8541EB03F2C342DCD2AE7E97889D4FE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_B4420EBD4066C98075C0E7E97888F2D2" xlink:to="loc_us-gaap_SubsequentEventMember_E8541EB03F2C342DCD2AE7E97889D4FE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_VariableRateAxis" xlink:label="loc_us-gaap_VariableRateAxis_A5AB8F65FF0910E851DFE7E97889D2C7" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_A8084CC9E34BAFD13174E7E978879A52" xlink:to="loc_us-gaap_VariableRateAxis_A5AB8F65FF0910E851DFE7E97889D2C7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_VariableRateDomain" xlink:label="loc_us-gaap_VariableRateDomain_1B782659838188DE9A3DE7E97889E786_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableRateAxis_A5AB8F65FF0910E851DFE7E97889D2C7" xlink:to="loc_us-gaap_VariableRateDomain_1B782659838188DE9A3DE7E97889E786_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_VariableRateDomain" xlink:label="loc_us-gaap_VariableRateDomain_1B782659838188DE9A3DE7E97889E786" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableRateAxis_A5AB8F65FF0910E851DFE7E97889D2C7" xlink:to="loc_us-gaap_VariableRateDomain_1B782659838188DE9A3DE7E97889E786" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_ApplicableMarginMember" xlink:label="loc_prth_ApplicableMarginMember_32BD15BA12ADF912EFA7E7E97889CEDE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_1B782659838188DE9A3DE7E97889E786" xlink:to="loc_prth_ApplicableMarginMember_32BD15BA12ADF912EFA7E7E97889CEDE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeAxis" xlink:label="loc_srt_RangeAxis_2C20DC653F7F3370098FE7E9788A848F" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_A8084CC9E34BAFD13174E7E978879A52" xlink:to="loc_srt_RangeAxis_2C20DC653F7F3370098FE7E9788A848F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_DE7C59411C74A292D592E7E9788AE161_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_2C20DC653F7F3370098FE7E9788A848F" xlink:to="loc_srt_RangeMember_DE7C59411C74A292D592E7E9788AE161_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_DE7C59411C74A292D592E7E9788AE161" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_2C20DC653F7F3370098FE7E9788A848F" xlink:to="loc_srt_RangeMember_DE7C59411C74A292D592E7E9788AE161" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_MinimumMember" xlink:label="loc_srt_MinimumMember_7B0F7DCC943AB4F4B629E7E9788A3DD9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_DE7C59411C74A292D592E7E9788AE161" xlink:to="loc_srt_MinimumMember_7B0F7DCC943AB4F4B629E7E9788A3DD9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_MaximumMember" xlink:label="loc_srt_MaximumMember_526E696234944EB63A28E7E9788A3A86" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_DE7C59411C74A292D592E7E9788AE161" xlink:to="loc_srt_MaximumMember_526E696234944EB63A28E7E9788A3A86" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_StatementScenarioAxis" xlink:label="loc_srt_StatementScenarioAxis_DB98E8D6FEF6C6888EF5E7E9788A09D8" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_A8084CC9E34BAFD13174E7E978879A52" xlink:to="loc_srt_StatementScenarioAxis_DB98E8D6FEF6C6888EF5E7E9788A09D8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ScenarioUnspecifiedDomain" xlink:label="loc_srt_ScenarioUnspecifiedDomain_AB5BCA9FFB4ADBC27718E7E9788BD148_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementScenarioAxis_DB98E8D6FEF6C6888EF5E7E9788A09D8" xlink:to="loc_srt_ScenarioUnspecifiedDomain_AB5BCA9FFB4ADBC27718E7E9788BD148_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ScenarioUnspecifiedDomain" xlink:label="loc_srt_ScenarioUnspecifiedDomain_AB5BCA9FFB4ADBC27718E7E9788BD148" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementScenarioAxis_DB98E8D6FEF6C6888EF5E7E9788A09D8" xlink:to="loc_srt_ScenarioUnspecifiedDomain_AB5BCA9FFB4ADBC27718E7E9788BD148" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ScenarioForecastMember" xlink:label="loc_srt_ScenarioForecastMember_4127AAA1A3E537EA2432E7E9788B671A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ScenarioUnspecifiedDomain_AB5BCA9FFB4ADBC27718E7E9788BD148" xlink:to="loc_srt_ScenarioForecastMember_4127AAA1A3E537EA2432E7E9788B671A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentAxis" xlink:label="loc_us-gaap_DebtInstrumentAxis_59F78C166DBBAB85392BE7E9788B821E" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_A8084CC9E34BAFD13174E7E978879A52" xlink:to="loc_us-gaap_DebtInstrumentAxis_59F78C166DBBAB85392BE7E9788B821E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_0C23E1F69FED85F288C5E7E9788B7240_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_59F78C166DBBAB85392BE7E9788B821E" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_0C23E1F69FED85F288C5E7E9788B7240_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_0C23E1F69FED85F288C5E7E9788B7240" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_59F78C166DBBAB85392BE7E9788B821E" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_0C23E1F69FED85F288C5E7E9788B7240" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_DelayedDrawMember" xlink:label="loc_prth_DelayedDrawMember_9101C7A9A5B53176D834E7E9788C734C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_0C23E1F69FED85F288C5E7E9788B7240" xlink:to="loc_prth_DelayedDrawMember_9101C7A9A5B53176D834E7E9788C734C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditFacilityAxis" xlink:label="loc_us-gaap_LineOfCreditFacilityAxis_C0775852D7A9CE7D9078E7E9788C3A54" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_A8084CC9E34BAFD13174E7E978879A52" xlink:to="loc_us-gaap_LineOfCreditFacilityAxis_C0775852D7A9CE7D9078E7E9788C3A54" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditFacilityLenderDomain" xlink:label="loc_us-gaap_LineOfCreditFacilityLenderDomain_C97DE40E195D4BD371FAE7E9788CC27C_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LineOfCreditFacilityAxis_C0775852D7A9CE7D9078E7E9788C3A54" xlink:to="loc_us-gaap_LineOfCreditFacilityLenderDomain_C97DE40E195D4BD371FAE7E9788CC27C_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditFacilityLenderDomain" xlink:label="loc_us-gaap_LineOfCreditFacilityLenderDomain_C97DE40E195D4BD371FAE7E9788CC27C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LineOfCreditFacilityAxis_C0775852D7A9CE7D9078E7E9788C3A54" xlink:to="loc_us-gaap_LineOfCreditFacilityLenderDomain_C97DE40E195D4BD371FAE7E9788CC27C" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_GoldmanSachsSpecialtyLendingGroupMember" xlink:label="loc_prth_GoldmanSachsSpecialtyLendingGroupMember_F22D2C9511A87C2209F7E7E9788C3EFD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLenderDomain_C97DE40E195D4BD371FAE7E9788CC27C" xlink:to="loc_prth_GoldmanSachsSpecialtyLendingGroupMember_F22D2C9511A87C2209F7E7E9788C3EFD" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_SyndicateOfLendersMember" xlink:label="loc_prth_SyndicateOfLendersMember_CDF34B01E643FBDBC03FE7E9788DEC5F" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLenderDomain_C97DE40E195D4BD371FAE7E9788CC27C" xlink:to="loc_prth_SyndicateOfLendersMember_CDF34B01E643FBDBC03FE7E9788DEC5F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeAxis" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_C3ADFFB97A37681FEAFDE7E9788D113D" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_A8084CC9E34BAFD13174E7E978879A52" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_C3ADFFB97A37681FEAFDE7E9788D113D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_0EA84C98428653735F6DE7E9788D1DD6_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_C3ADFFB97A37681FEAFDE7E9788D113D" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_0EA84C98428653735F6DE7E9788D1DD6_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_0EA84C98428653735F6DE7E9788D1DD6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_C3ADFFB97A37681FEAFDE7E9788D113D" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_0EA84C98428653735F6DE7E9788D1DD6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditMember" xlink:label="loc_us-gaap_LineOfCreditMember_7D06209E6FB3C56F60A2E7E9788D1566" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_0EA84C98428653735F6DE7E9788D1DD6" xlink:to="loc_us-gaap_LineOfCreditMember_7D06209E6FB3C56F60A2E7E9788D1566" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LetterOfCreditMember" xlink:label="loc_us-gaap_LetterOfCreditMember_CC7EAFAFE3ADF420E173E7E9788E7E8A" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_0EA84C98428653735F6DE7E9788D1DD6" xlink:to="loc_us-gaap_LetterOfCreditMember_CC7EAFAFE3ADF420E173E7E9788E7E8A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CreditFacilityAxis" xlink:label="loc_us-gaap_CreditFacilityAxis_1797096907D4BD27F6A2E7E9788EA204" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_A8084CC9E34BAFD13174E7E978879A52" xlink:to="loc_us-gaap_CreditFacilityAxis_1797096907D4BD27F6A2E7E9788EA204" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CreditFacilityDomain" xlink:label="loc_us-gaap_CreditFacilityDomain_5BB67AA467EFFFDDA7D6E7E9788EA690_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_1797096907D4BD27F6A2E7E9788EA204" xlink:to="loc_us-gaap_CreditFacilityDomain_5BB67AA467EFFFDDA7D6E7E9788EA690_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CreditFacilityDomain" xlink:label="loc_us-gaap_CreditFacilityDomain_5BB67AA467EFFFDDA7D6E7E9788EA690" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_1797096907D4BD27F6A2E7E9788EA204" xlink:to="loc_us-gaap_CreditFacilityDomain_5BB67AA467EFFFDDA7D6E7E9788EA690" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevolvingCreditFacilityMember" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_304BCB03B57CBC0ED942E7E9788F3AFA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_5BB67AA467EFFFDDA7D6E7E9788EA690" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_304BCB03B57CBC0ED942E7E9788F3AFA" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_SwingLineFacilityMember" xlink:label="loc_prth_SwingLineFacilityMember_401797B43713A92F41C7E7E9788F35FB" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_5BB67AA467EFFFDDA7D6E7E9788EA690" xlink:to="loc_prth_SwingLineFacilityMember_401797B43713A92F41C7E7E9788F35FB" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_TermLoanMember" xlink:label="loc_prth_TermLoanMember_B867013276BD96A3EFF1E7E9788F1135" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_5BB67AA467EFFFDDA7D6E7E9788EA690" xlink:to="loc_prth_TermLoanMember_B867013276BD96A3EFF1E7E9788F1135" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_12ED5497F836FA9B3931E7E9788FB2AA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_A5B3A0FD41A00FB8A0DFE7E9788F1A78" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_12ED5497F836FA9B3931E7E9788FB2AA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity" xlink:label="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_D68A7795300F92085820E7E978902357" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_A5B3A0FD41A00FB8A0DFE7E9788F1A78" xlink:to="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_D68A7795300F92085820E7E978902357" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_DebtInstrumentInterestRateLIBORFloor" xlink:label="loc_prth_DebtInstrumentInterestRateLIBORFloor_7F9DEA8D45955484AD59E7E97890C36C" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_A5B3A0FD41A00FB8A0DFE7E9788F1A78" xlink:to="loc_prth_DebtInstrumentInterestRateLIBORFloor_7F9DEA8D45955484AD59E7E97890C36C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage" xlink:label="loc_us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage_BC03F744B5189529B40DE7E978903EBE" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_A5B3A0FD41A00FB8A0DFE7E9788F1A78" xlink:to="loc_us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage_BC03F744B5189529B40DE7E978903EBE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_2439788C582362627917E7E97890AFFA" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_A5B3A0FD41A00FB8A0DFE7E9788F1A78" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_2439788C582362627917E7E97890AFFA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentInterestRateEffectivePercentage" xlink:label="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_F1F394A0ACF8DA55E757E7E978915BDD" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_A5B3A0FD41A00FB8A0DFE7E9788F1A78" xlink:to="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_F1F394A0ACF8DA55E757E7E978915BDD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentInterestRateIncreaseDecrease" xlink:label="loc_us-gaap_DebtInstrumentInterestRateIncreaseDecrease_F41C29DEE3EC3EF8A3ACE7E97890DA24" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_A5B3A0FD41A00FB8A0DFE7E9788F1A78" xlink:to="loc_us-gaap_DebtInstrumentInterestRateIncreaseDecrease_F41C29DEE3EC3EF8A3ACE7E97890DA24" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentPeriodicPaymentPrincipal" xlink:label="loc_us-gaap_DebtInstrumentPeriodicPaymentPrincipal_A40CD6230C032439EFE7E7E978919AF7" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_A5B3A0FD41A00FB8A0DFE7E9788F1A78" xlink:to="loc_us-gaap_DebtInstrumentPeriodicPaymentPrincipal_A40CD6230C032439EFE7E7E978919AF7" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_LineOfCreditFaciityPenaltyPercentageOnDefaultPrincipalPrepayments" xlink:label="loc_prth_LineOfCreditFaciityPenaltyPercentageOnDefaultPrincipalPrepayments_CD6E4F89D2295490E718E7E97891BDC3" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_A5B3A0FD41A00FB8A0DFE7E9788F1A78" xlink:to="loc_prth_LineOfCreditFaciityPenaltyPercentageOnDefaultPrincipalPrepayments_CD6E4F89D2295490E718E7E97891BDC3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestExpense" xlink:label="loc_us-gaap_InterestExpense_0B6ADB2D75F61179C618E7E978911C32" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_A5B3A0FD41A00FB8A0DFE7E9788F1A78" xlink:to="loc_us-gaap_InterestExpense_0B6ADB2D75F61179C618E7E978911C32" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCredit" xlink:label="loc_us-gaap_LineOfCredit_F95717EDF164D845CB96E7E978913B30" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_A5B3A0FD41A00FB8A0DFE7E9788F1A78" xlink:to="loc_us-gaap_LineOfCredit_F95717EDF164D845CB96E7E978913B30" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestPayableCurrentAndNoncurrent" xlink:label="loc_us-gaap_InterestPayableCurrentAndNoncurrent_6BA2A23C758AF34B6E19E7E97891D3B6" xlink:type="locator" />
    <link:definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_A5B3A0FD41A00FB8A0DFE7E9788F1A78" xlink:to="loc_us-gaap_InterestPayableCurrentAndNoncurrent_6BA2A23C758AF34B6E19E7E97891D3B6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PaidInKindInterest" xlink:label="loc_us-gaap_PaidInKindInterest_25E1F10F0A9A54242F30E7E9789204FE" xlink:type="locator" />
    <link:definitionArc order="13" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_A5B3A0FD41A00FB8A0DFE7E9788F1A78" xlink:to="loc_us-gaap_PaidInKindInterest_25E1F10F0A9A54242F30E7E9789204FE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditFacilityCommitmentFeeAmount" xlink:label="loc_us-gaap_LineOfCreditFacilityCommitmentFeeAmount_F82DDF083DEFC5736A35E7E978923501" xlink:type="locator" />
    <link:definitionArc order="14" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_A5B3A0FD41A00FB8A0DFE7E9788F1A78" xlink:to="loc_us-gaap_LineOfCreditFacilityCommitmentFeeAmount_F82DDF083DEFC5736A35E7E978923501" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_CapitalizedLenderFees" xlink:label="loc_prth_CapitalizedLenderFees_7D6017AFC2436569C4A8E7E97892179E" xlink:type="locator" />
    <link:definitionArc order="15" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_A5B3A0FD41A00FB8A0DFE7E9788F1A78" xlink:to="loc_prth_CapitalizedLenderFees_7D6017AFC2436569C4A8E7E97892179E" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_DebtInstrumentUnamortizedDiscountIncludingCapitalizedFees.NetOfAmortizationExpense" xlink:label="loc_prth_DebtInstrumentUnamortizedDiscountIncludingCapitalizedFees.NetOfAmortizationExpense_2199765DBF7127838AF4E7E9789277FC" xlink:type="locator" />
    <link:definitionArc order="16" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_A5B3A0FD41A00FB8A0DFE7E9788F1A78" xlink:to="loc_prth_DebtInstrumentUnamortizedDiscountIncludingCapitalizedFees.NetOfAmortizationExpense_2199765DBF7127838AF4E7E9789277FC" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_AmortizationOfDebtDiscountPremiumAndDebtIssuanceCosts" xlink:label="loc_prth_AmortizationOfDebtDiscountPremiumAndDebtIssuanceCosts_C7A250E5B41E94D9281FE7E97892A38B" xlink:type="locator" />
    <link:definitionArc order="17" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_A5B3A0FD41A00FB8A0DFE7E9788F1A78" xlink:to="loc_prth_AmortizationOfDebtDiscountPremiumAndDebtIssuanceCosts_C7A250E5B41E94D9281FE7E97892A38B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtRelatedCommitmentFeesAndDebtIssuanceCosts" xlink:label="loc_us-gaap_DebtRelatedCommitmentFeesAndDebtIssuanceCosts_750A1EB3B372564AC067E7E97892E567" xlink:type="locator" />
    <link:definitionArc order="18" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_A5B3A0FD41A00FB8A0DFE7E9788F1A78" xlink:to="loc_us-gaap_DebtRelatedCommitmentFeesAndDebtIssuanceCosts_750A1EB3B372564AC067E7E97892E567" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_DebtCovenantMaximumNetLeverageRatio" xlink:label="loc_prth_DebtCovenantMaximumNetLeverageRatio_FD80D966BF18EDA6AEFEE7E97893431A" xlink:type="locator" />
    <link:definitionArc order="19" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_A5B3A0FD41A00FB8A0DFE7E9788F1A78" xlink:to="loc_prth_DebtCovenantMaximumNetLeverageRatio_FD80D966BF18EDA6AEFEE7E97893431A" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://miacquisitions.com/role/DebtObligationsRollingMaturitiesOfLongTermDebtDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentLineItems" xlink:label="loc_us-gaap_DebtInstrumentLineItems_713FB31EC0F407F2D9DBD99ECE2F08B0" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentTable" xlink:label="loc_us-gaap_DebtInstrumentTable_7F7E4353C48DF0E02E39D99ECE20787F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_713FB31EC0F407F2D9DBD99ECE2F08B0" xlink:to="loc_us-gaap_DebtInstrumentTable_7F7E4353C48DF0E02E39D99ECE20787F" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeAxis" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_02E687F4FBB51A1A57BFD99ECE21AE20" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_7F7E4353C48DF0E02E39D99ECE20787F" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_02E687F4FBB51A1A57BFD99ECE21AE20" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_9CD05A309FE0F0869620D99ECE2281A8_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_02E687F4FBB51A1A57BFD99ECE21AE20" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_9CD05A309FE0F0869620D99ECE2281A8_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_9CD05A309FE0F0869620D99ECE2281A8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_02E687F4FBB51A1A57BFD99ECE21AE20" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_9CD05A309FE0F0869620D99ECE2281A8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditMember" xlink:label="loc_us-gaap_LineOfCreditMember_9660CFBA6631BF9FA223D99ECE231122" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_9CD05A309FE0F0869620D99ECE2281A8" xlink:to="loc_us-gaap_LineOfCreditMember_9660CFBA6631BF9FA223D99ECE231122" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditFacilityAxis" xlink:label="loc_us-gaap_LineOfCreditFacilityAxis_95327E8B05844BBC66C6D99ECE293634" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_7F7E4353C48DF0E02E39D99ECE20787F" xlink:to="loc_us-gaap_LineOfCreditFacilityAxis_95327E8B05844BBC66C6D99ECE293634" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditFacilityLenderDomain" xlink:label="loc_us-gaap_LineOfCreditFacilityLenderDomain_5009DDE7EA31459090AED99ECE29DB41_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LineOfCreditFacilityAxis_95327E8B05844BBC66C6D99ECE293634" xlink:to="loc_us-gaap_LineOfCreditFacilityLenderDomain_5009DDE7EA31459090AED99ECE29DB41_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditFacilityLenderDomain" xlink:label="loc_us-gaap_LineOfCreditFacilityLenderDomain_5009DDE7EA31459090AED99ECE29DB41" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LineOfCreditFacilityAxis_95327E8B05844BBC66C6D99ECE293634" xlink:to="loc_us-gaap_LineOfCreditFacilityLenderDomain_5009DDE7EA31459090AED99ECE29DB41" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_SyndicateOfLendersMember" xlink:label="loc_prth_SyndicateOfLendersMember_74266FF6D042FF06A27AD99ECE2B0C6E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLenderDomain_5009DDE7EA31459090AED99ECE29DB41" xlink:to="loc_prth_SyndicateOfLendersMember_74266FF6D042FF06A27AD99ECE2B0C6E" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_GoldmanSachsSpecialtyLendingGroupMember" xlink:label="loc_prth_GoldmanSachsSpecialtyLendingGroupMember_EA00B5DA41816F7DFFF9D99ECE2C6F6A" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLenderDomain_5009DDE7EA31459090AED99ECE29DB41" xlink:to="loc_prth_GoldmanSachsSpecialtyLendingGroupMember_EA00B5DA41816F7DFFF9D99ECE2C6F6A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CreditFacilityAxis" xlink:label="loc_us-gaap_CreditFacilityAxis_552C47FF86ADE3DF65F9D99ECE2ECF53" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_7F7E4353C48DF0E02E39D99ECE20787F" xlink:to="loc_us-gaap_CreditFacilityAxis_552C47FF86ADE3DF65F9D99ECE2ECF53" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CreditFacilityDomain" xlink:label="loc_us-gaap_CreditFacilityDomain_B4B9CDC717DD38B52B72D99ECE2EB02A_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_552C47FF86ADE3DF65F9D99ECE2ECF53" xlink:to="loc_us-gaap_CreditFacilityDomain_B4B9CDC717DD38B52B72D99ECE2EB02A_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CreditFacilityDomain" xlink:label="loc_us-gaap_CreditFacilityDomain_B4B9CDC717DD38B52B72D99ECE2EB02A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_552C47FF86ADE3DF65F9D99ECE2ECF53" xlink:to="loc_us-gaap_CreditFacilityDomain_B4B9CDC717DD38B52B72D99ECE2EB02A" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_TermLoanMember" xlink:label="loc_prth_TermLoanMember_E1C60E1D7CD23BF255A1D99ECE2E1B6F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_B4B9CDC717DD38B52B72D99ECE2EB02A" xlink:to="loc_prth_TermLoanMember_E1C60E1D7CD23BF255A1D99ECE2E1B6F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevolvingCreditFacilityMember" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_D2E9026364BDA62869B9D99ECE2F56F6" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_B4B9CDC717DD38B52B72D99ECE2EB02A" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_D2E9026364BDA62869B9D99ECE2F56F6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextRollingTwelveMonths" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextRollingTwelveMonths_B19CD3BD04AD0D03685BD99ECE30F16A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_713FB31EC0F407F2D9DBD99ECE2F08B0" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextRollingTwelveMonths_B19CD3BD04AD0D03685BD99ECE30F16A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInRollingYearTwo" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInRollingYearTwo_D3B6D24F1345446692BDD99ECE31BC3D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_713FB31EC0F407F2D9DBD99ECE2F08B0" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInRollingYearTwo_D3B6D24F1345446692BDD99ECE31BC3D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInRollingYearThree" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInRollingYearThree_A57466B0A8A6A7F4707FD99ECE3264A6" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_713FB31EC0F407F2D9DBD99ECE2F08B0" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInRollingYearThree_A57466B0A8A6A7F4707FD99ECE3264A6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInRollingYearFour" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInRollingYearFour_955DE1AD3DFDE58CE5F2D99ECE326069" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_713FB31EC0F407F2D9DBD99ECE2F08B0" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInRollingYearFour_955DE1AD3DFDE58CE5F2D99ECE326069" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentCarryingAmount" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_BD3FC6288E94ED7C5025D99ECE33A93F" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_713FB31EC0F407F2D9DBD99ECE2F08B0" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_BD3FC6288E94ED7C5025D99ECE33A93F" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://miacquisitions.com/role/DebtObligationsScheduleOfLongTermDebtDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentLineItems" xlink:label="loc_us-gaap_DebtInstrumentLineItems_D845081E149284F80980D99ED0365CC8" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentTable" xlink:label="loc_us-gaap_DebtInstrumentTable_FCAC07BFE0E86CA7F895D99ED0172F06" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_D845081E149284F80980D99ED0365CC8" xlink:to="loc_us-gaap_DebtInstrumentTable_FCAC07BFE0E86CA7F895D99ED0172F06" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentAxis" xlink:label="loc_us-gaap_DebtInstrumentAxis_EE8168711B9B9CFB7CECD99ED01996C9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_FCAC07BFE0E86CA7F895D99ED0172F06" xlink:to="loc_us-gaap_DebtInstrumentAxis_EE8168711B9B9CFB7CECD99ED01996C9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_75F54781B21CFE1C238FD99ED01E41B1_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_EE8168711B9B9CFB7CECD99ED01996C9" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_75F54781B21CFE1C238FD99ED01E41B1_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_75F54781B21CFE1C238FD99ED01E41B1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_EE8168711B9B9CFB7CECD99ED01996C9" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_75F54781B21CFE1C238FD99ED01E41B1" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_SeniorTermLoanMaturingJanuary32023Member" xlink:label="loc_prth_SeniorTermLoanMaturingJanuary32023Member_0A27BDE8DF45C1622A2AD99ED01F8FC6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_75F54781B21CFE1C238FD99ED01E41B1" xlink:to="loc_prth_SeniorTermLoanMaturingJanuary32023Member_0A27BDE8DF45C1622A2AD99ED01F8FC6" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_SubordinatedTermLoanMaturingJuly32023Member" xlink:label="loc_prth_SubordinatedTermLoanMaturingJuly32023Member_62FCD6D7D0F840574780D99ED021A988" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_75F54781B21CFE1C238FD99ED01E41B1" xlink:to="loc_prth_SubordinatedTermLoanMaturingJuly32023Member_62FCD6D7D0F840574780D99ED021A988" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditFacilityAxis" xlink:label="loc_us-gaap_LineOfCreditFacilityAxis_338789113F173BEF3857D99ED0219023" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_FCAC07BFE0E86CA7F895D99ED0172F06" xlink:to="loc_us-gaap_LineOfCreditFacilityAxis_338789113F173BEF3857D99ED0219023" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditFacilityLenderDomain" xlink:label="loc_us-gaap_LineOfCreditFacilityLenderDomain_5CAD6E1363D5AE54148CD99ED024DE6E_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LineOfCreditFacilityAxis_338789113F173BEF3857D99ED0219023" xlink:to="loc_us-gaap_LineOfCreditFacilityLenderDomain_5CAD6E1363D5AE54148CD99ED024DE6E_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditFacilityLenderDomain" xlink:label="loc_us-gaap_LineOfCreditFacilityLenderDomain_5CAD6E1363D5AE54148CD99ED024DE6E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LineOfCreditFacilityAxis_338789113F173BEF3857D99ED0219023" xlink:to="loc_us-gaap_LineOfCreditFacilityLenderDomain_5CAD6E1363D5AE54148CD99ED024DE6E" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_SyndicateOfLendersMember" xlink:label="loc_prth_SyndicateOfLendersMember_E7009FE65FEB6378865DD99ED0247E2E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLenderDomain_5CAD6E1363D5AE54148CD99ED024DE6E" xlink:to="loc_prth_SyndicateOfLendersMember_E7009FE65FEB6378865DD99ED0247E2E" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_GoldmanSachsSpecialtyLendingGroupMember" xlink:label="loc_prth_GoldmanSachsSpecialtyLendingGroupMember_1DB017EAA1F8BC87FA7ED99ED025D43B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLenderDomain_5CAD6E1363D5AE54148CD99ED024DE6E" xlink:to="loc_prth_GoldmanSachsSpecialtyLendingGroupMember_1DB017EAA1F8BC87FA7ED99ED025D43B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeAxis" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_6EE798EC82995BD59D8ED99ED0255F52" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_FCAC07BFE0E86CA7F895D99ED0172F06" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_6EE798EC82995BD59D8ED99ED0255F52" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_B39EAEFAFC1E3105E702D99ED025F288_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_6EE798EC82995BD59D8ED99ED0255F52" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_B39EAEFAFC1E3105E702D99ED025F288_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_B39EAEFAFC1E3105E702D99ED025F288" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_6EE798EC82995BD59D8ED99ED0255F52" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_B39EAEFAFC1E3105E702D99ED025F288" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SeniorNotesMember" xlink:label="loc_us-gaap_SeniorNotesMember_9E9D26548E66D28AFD8BD99ED0266CFC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_B39EAEFAFC1E3105E702D99ED025F288" xlink:to="loc_us-gaap_SeniorNotesMember_9E9D26548E66D28AFD8BD99ED0266CFC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditMember" xlink:label="loc_us-gaap_LineOfCreditMember_560636425C98A971F10AD99ED028ABF1" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_B39EAEFAFC1E3105E702D99ED025F288" xlink:to="loc_us-gaap_LineOfCreditMember_560636425C98A971F10AD99ED028ABF1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubordinatedDebtMember" xlink:label="loc_us-gaap_SubordinatedDebtMember_9300E3504C9A3D4CC4DFD99ED0286C5C" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_B39EAEFAFC1E3105E702D99ED025F288" xlink:to="loc_us-gaap_SubordinatedDebtMember_9300E3504C9A3D4CC4DFD99ED0286C5C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CreditFacilityAxis" xlink:label="loc_us-gaap_CreditFacilityAxis_13295159560F9B11E725D99ED02ACCC7" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_FCAC07BFE0E86CA7F895D99ED0172F06" xlink:to="loc_us-gaap_CreditFacilityAxis_13295159560F9B11E725D99ED02ACCC7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CreditFacilityDomain" xlink:label="loc_us-gaap_CreditFacilityDomain_F36E56085E9969907609D99ED030F0DC_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_13295159560F9B11E725D99ED02ACCC7" xlink:to="loc_us-gaap_CreditFacilityDomain_F36E56085E9969907609D99ED030F0DC_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CreditFacilityDomain" xlink:label="loc_us-gaap_CreditFacilityDomain_F36E56085E9969907609D99ED030F0DC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_13295159560F9B11E725D99ED02ACCC7" xlink:to="loc_us-gaap_CreditFacilityDomain_F36E56085E9969907609D99ED030F0DC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevolvingCreditFacilityMember" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_B7C365A11B5EE67DCB12D99ED0302B90" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_F36E56085E9969907609D99ED030F0DC" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_B7C365A11B5EE67DCB12D99ED0302B90" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LetterOfCreditMember" xlink:label="loc_us-gaap_LetterOfCreditMember_63E6E7539681DA659AA0D99ED031BFCE" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_F36E56085E9969907609D99ED030F0DC" xlink:to="loc_us-gaap_LetterOfCreditMember_63E6E7539681DA659AA0D99ED031BFCE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_VariableRateAxis" xlink:label="loc_us-gaap_VariableRateAxis_74A14F391FF6BA3BE8EED99ED031EA07" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_FCAC07BFE0E86CA7F895D99ED0172F06" xlink:to="loc_us-gaap_VariableRateAxis_74A14F391FF6BA3BE8EED99ED031EA07" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_VariableRateDomain" xlink:label="loc_us-gaap_VariableRateDomain_0F65570F81D9D734BD7BD99ED033F97F_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableRateAxis_74A14F391FF6BA3BE8EED99ED031EA07" xlink:to="loc_us-gaap_VariableRateDomain_0F65570F81D9D734BD7BD99ED033F97F_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_VariableRateDomain" xlink:label="loc_us-gaap_VariableRateDomain_0F65570F81D9D734BD7BD99ED033F97F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableRateAxis_74A14F391FF6BA3BE8EED99ED031EA07" xlink:to="loc_us-gaap_VariableRateDomain_0F65570F81D9D734BD7BD99ED033F97F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LondonInterbankOfferedRateLIBORMember" xlink:label="loc_us-gaap_LondonInterbankOfferedRateLIBORMember_010FA84BF21A42DC1EB1D99ED0347C1A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_0F65570F81D9D734BD7BD99ED033F97F" xlink:to="loc_us-gaap_LondonInterbankOfferedRateLIBORMember_010FA84BF21A42DC1EB1D99ED0347C1A" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_PaymentInKindInterestRateMember" xlink:label="loc_prth_PaymentInKindInterestRateMember_E485A713EED837A57315D99ED034F5AA" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_0F65570F81D9D734BD7BD99ED033F97F" xlink:to="loc_prth_PaymentInKindInterestRateMember_E485A713EED837A57315D99ED034F5AA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentCarryingAmount" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_20643B518C3C49A9248DD99ED03602B1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_D845081E149284F80980D99ED0365CC8" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_20643B518C3C49A9248DD99ED03602B1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongTermDebtCurrent" xlink:label="loc_us-gaap_LongTermDebtCurrent_45C9BD4B1575F17265ECD99ED0366C13" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_D845081E149284F80980D99ED0365CC8" xlink:to="loc_us-gaap_LongTermDebtCurrent_45C9BD4B1575F17265ECD99ED0366C13" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentUnamortizedDiscount" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedDiscount_8E6E79DB1B27C37A6E2BD99ED0376DD5" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_D845081E149284F80980D99ED0365CC8" xlink:to="loc_us-gaap_DebtInstrumentUnamortizedDiscount_8E6E79DB1B27C37A6E2BD99ED0376DD5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongTermDebt" xlink:label="loc_us-gaap_LongTermDebt_27B52D3AE219110BCCECD99ED038ED6F" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_D845081E149284F80980D99ED0365CC8" xlink:to="loc_us-gaap_LongTermDebt_27B52D3AE219110BCCECD99ED038ED6F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_AC9C183ADA2AE0589655D99ED03A0D98" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_D845081E149284F80980D99ED0365CC8" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_AC9C183ADA2AE0589655D99ED03A0D98" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd" xlink:label="loc_us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd_04214FF71BBCA4A7423ED99ED03A1DEA" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_D845081E149284F80980D99ED0365CC8" xlink:to="loc_us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd_04214FF71BBCA4A7423ED99ED03A1DEA" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://miacquisitions.com/role/DebtObligationsTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://miacquisitions.com/role/FairValue" xlink:type="extended" />
  <link:definitionLink xlink:role="http://miacquisitions.com/role/FairValueNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_7F7CA9F2921F6F7C2B14D9CCEB1F8296" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_A859F65B32801BDE0F8AD9CCEB1A8BE1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_7F7CA9F2921F6F7C2B14D9CCEB1F8296" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_A859F65B32801BDE0F8AD9CCEB1A8BE1" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeAxis" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_79FBDA3392590EA3E494D9CCEB1B40BF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_A859F65B32801BDE0F8AD9CCEB1A8BE1" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_79FBDA3392590EA3E494D9CCEB1B40BF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_056F22A1132865C25A75D9CCEB1BEB34_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_79FBDA3392590EA3E494D9CCEB1B40BF" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_056F22A1132865C25A75D9CCEB1BEB34_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_056F22A1132865C25A75D9CCEB1BEB34" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_79FBDA3392590EA3E494D9CCEB1B40BF" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_056F22A1132865C25A75D9CCEB1BEB34" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SeniorNotesMember" xlink:label="loc_us-gaap_SeniorNotesMember_6E9406C5E63A34DE48EBD9CCEB1B1E4C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_056F22A1132865C25A75D9CCEB1BEB34" xlink:to="loc_us-gaap_SeniorNotesMember_6E9406C5E63A34DE48EBD9CCEB1B1E4C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentAxis" xlink:label="loc_us-gaap_DebtInstrumentAxis_43A3A297F989D7967F90D9CCEB1B3899" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_A859F65B32801BDE0F8AD9CCEB1A8BE1" xlink:to="loc_us-gaap_DebtInstrumentAxis_43A3A297F989D7967F90D9CCEB1B3899" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_155703BCA285720A25E8D9CCEB1C5824_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_43A3A297F989D7967F90D9CCEB1B3899" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_155703BCA285720A25E8D9CCEB1C5824_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_155703BCA285720A25E8D9CCEB1C5824" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_43A3A297F989D7967F90D9CCEB1B3899" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_155703BCA285720A25E8D9CCEB1C5824" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_SeniorTermLoanMaturingJanuary32023Member" xlink:label="loc_prth_SeniorTermLoanMaturingJanuary32023Member_56F41C994848A850FCC6D9CCEB1C37BE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_155703BCA285720A25E8D9CCEB1C5824" xlink:to="loc_prth_SeniorTermLoanMaturingJanuary32023Member_56F41C994848A850FCC6D9CCEB1C37BE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeAxis" xlink:label="loc_srt_RangeAxis_204DAFB64417DBCA64ECD9CCEB1CC686" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_A859F65B32801BDE0F8AD9CCEB1A8BE1" xlink:to="loc_srt_RangeAxis_204DAFB64417DBCA64ECD9CCEB1CC686" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_94452B3F71FFF66BD33CD9CCEB1C2BA1_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_204DAFB64417DBCA64ECD9CCEB1CC686" xlink:to="loc_srt_RangeMember_94452B3F71FFF66BD33CD9CCEB1C2BA1_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_94452B3F71FFF66BD33CD9CCEB1C2BA1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_204DAFB64417DBCA64ECD9CCEB1CC686" xlink:to="loc_srt_RangeMember_94452B3F71FFF66BD33CD9CCEB1C2BA1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_MinimumMember" xlink:label="loc_srt_MinimumMember_4E73609994EF05D30A2ED9CCEB1DE761" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_94452B3F71FFF66BD33CD9CCEB1C2BA1" xlink:to="loc_srt_MinimumMember_4E73609994EF05D30A2ED9CCEB1DE761" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_MaximumMember" xlink:label="loc_srt_MaximumMember_27F94877157EEBA6A261D9CCEB1DBF48" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_94452B3F71FFF66BD33CD9CCEB1C2BA1" xlink:to="loc_srt_MaximumMember_27F94877157EEBA6A261D9CCEB1DBF48" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_72ACBABDE2E460327006D9CCEB1D76E2" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_A859F65B32801BDE0F8AD9CCEB1A8BE1" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_72ACBABDE2E460327006D9CCEB1D76E2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_B35603A86C05713ACF2ED9CCEB1D38C8_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_72ACBABDE2E460327006D9CCEB1D76E2" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_B35603A86C05713ACF2ED9CCEB1D38C8_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_B35603A86C05713ACF2ED9CCEB1D38C8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_72ACBABDE2E460327006D9CCEB1D76E2" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_B35603A86C05713ACF2ED9CCEB1D38C8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueInputsLevel3Member" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_56A8DE7D9AAE740BA1B4D9CCEB1E12F7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_B35603A86C05713ACF2ED9CCEB1D38C8" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_56A8DE7D9AAE740BA1B4D9CCEB1E12F7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAxis" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_F616CEF05851F8F5E10DD9CCEB1E4468" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_A859F65B32801BDE0F8AD9CCEB1A8BE1" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_F616CEF05851F8F5E10DD9CCEB1E4468" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_4D84DE6CB64E9A8EBF0AD9CCEB1E514F_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_F616CEF05851F8F5E10DD9CCEB1E4468" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_4D84DE6CB64E9A8EBF0AD9CCEB1E514F_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_4D84DE6CB64E9A8EBF0AD9CCEB1E514F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_F616CEF05851F8F5E10DD9CCEB1E4468" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_4D84DE6CB64E9A8EBF0AD9CCEB1E514F" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_PriorityPaymentSystemsTechPartnerMember" xlink:label="loc_prth_PriorityPaymentSystemsTechPartnerMember_A670F54F8D22B1446DE0D9CCEB1EE54A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_4D84DE6CB64E9A8EBF0AD9CCEB1E514F" xlink:to="loc_prth_PriorityPaymentSystemsTechPartnerMember_A670F54F8D22B1446DE0D9CCEB1EE54A" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_PriorityPaymentSystemsNortheastMember" xlink:label="loc_prth_PriorityPaymentSystemsNortheastMember_ADB49A2E6647180C688ED9CCEB1F000C" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_4D84DE6CB64E9A8EBF0AD9CCEB1E514F" xlink:to="loc_prth_PriorityPaymentSystemsNortheastMember_ADB49A2E6647180C688ED9CCEB1F000C" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_BusinessCombinationContingentConsiderationWeightedPayoutProbabilityPercentage" xlink:label="loc_prth_BusinessCombinationContingentConsiderationWeightedPayoutProbabilityPercentage_A0DB0B402518C8685497D9CCEB1F44B8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_7F7CA9F2921F6F7C2B14D9CCEB1F8296" xlink:to="loc_prth_BusinessCombinationContingentConsiderationWeightedPayoutProbabilityPercentage_A0DB0B402518C8685497D9CCEB1F44B8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationContingentConsiderationLiability" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationLiability_D589541F85142AB60C46D9CCEB1F8307" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_7F7CA9F2921F6F7C2B14D9CCEB1F8296" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationLiability_D589541F85142AB60C46D9CCEB1F8307" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_BusinessCombinationContingentConsiderationLiabilityFairValueDisclosure" xlink:label="loc_prth_BusinessCombinationContingentConsiderationLiabilityFairValueDisclosure_9C3D678E65DB8E6E34A4D9CCEB2073D1" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_7F7CA9F2921F6F7C2B14D9CCEB1F8296" xlink:to="loc_prth_BusinessCombinationContingentConsiderationLiabilityFairValueDisclosure_9C3D678E65DB8E6E34A4D9CCEB2073D1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NotesReceivableFairValueDisclosure" xlink:label="loc_us-gaap_NotesReceivableFairValueDisclosure_D9CB314968036464042FD9CCEB2072F7" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_7F7CA9F2921F6F7C2B14D9CCEB1F8296" xlink:to="loc_us-gaap_NotesReceivableFairValueDisclosure_D9CB314968036464042FD9CCEB2072F7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongTermDebtFairValue" xlink:label="loc_us-gaap_LongTermDebtFairValue_A9220D764F6EFC1ACDF9D9CCEB201FC9" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_7F7CA9F2921F6F7C2B14D9CCEB1F8296" xlink:to="loc_us-gaap_LongTermDebtFairValue_A9220D764F6EFC1ACDF9D9CCEB201FC9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentCarryingAmount" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_5CB55F9F4855313D5A3AD9CCEB20E265" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_7F7CA9F2921F6F7C2B14D9CCEB1F8296" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_5CB55F9F4855313D5A3AD9CCEB20E265" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://miacquisitions.com/role/GoodwillAndIntangibleAssets" xlink:type="extended" />
  <link:definitionLink xlink:role="http://miacquisitions.com/role/GoodwillAndIntangibleAssetsGoodwillAllocationDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_GoodwillLineItems" xlink:label="loc_us-gaap_GoodwillLineItems_EB8E25DF4B95766E6C8BD99ED28C283F" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfGoodwillTable" xlink:label="loc_us-gaap_ScheduleOfGoodwillTable_1F4C5A886C10C57041E1D99ED28620D3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_GoodwillLineItems_EB8E25DF4B95766E6C8BD99ED28C283F" xlink:to="loc_us-gaap_ScheduleOfGoodwillTable_1F4C5A886C10C57041E1D99ED28620D3" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_DABF1E237D355B90C192D99ED287B520" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGoodwillTable_1F4C5A886C10C57041E1D99ED28620D3" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_DABF1E237D355B90C192D99ED287B520" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_76BEB6C5C4FF7E5A8646D99ED2892E09_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_DABF1E237D355B90C192D99ED287B520" xlink:to="loc_us-gaap_SegmentDomain_76BEB6C5C4FF7E5A8646D99ED2892E09_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_76BEB6C5C4FF7E5A8646D99ED2892E09" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_DABF1E237D355B90C192D99ED287B520" xlink:to="loc_us-gaap_SegmentDomain_76BEB6C5C4FF7E5A8646D99ED2892E09" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_ConsumerPaymentsMember" xlink:label="loc_prth_ConsumerPaymentsMember_F653B041F68150703EBBD99ED289FD1F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_76BEB6C5C4FF7E5A8646D99ED2892E09" xlink:to="loc_prth_ConsumerPaymentsMember_F653B041F68150703EBBD99ED289FD1F" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_IntegratedPartnersMember" xlink:label="loc_prth_IntegratedPartnersMember_C5E502D82DD285223766D99ED28B0C93" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_76BEB6C5C4FF7E5A8646D99ED2892E09" xlink:to="loc_prth_IntegratedPartnersMember_C5E502D82DD285223766D99ED28B0C93" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_Goodwill" xlink:label="loc_us-gaap_Goodwill_05E1A9B25165AF4300AFD99ED28CC98A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_EB8E25DF4B95766E6C8BD99ED28C283F" xlink:to="loc_us-gaap_Goodwill_05E1A9B25165AF4300AFD99ED28CC98A" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://miacquisitions.com/role/GoodwillAndIntangibleAssetsIntangibleAssetsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_273260E50C1C2D2FEC05D99ED1D1B502" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_951BA16AFB858AC1A5A4D99ED1C4D1A0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_273260E50C1C2D2FEC05D99ED1D1B502" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_951BA16AFB858AC1A5A4D99ED1C4D1A0" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_69B165AB282FB85B59D0D99ED1CA76CF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_951BA16AFB858AC1A5A4D99ED1C4D1A0" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_69B165AB282FB85B59D0D99ED1CA76CF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_770854EC5EE7BFA210E8D99ED1CC5820_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_69B165AB282FB85B59D0D99ED1CA76CF" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_770854EC5EE7BFA210E8D99ED1CC5820_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_770854EC5EE7BFA210E8D99ED1CC5820" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_69B165AB282FB85B59D0D99ED1CA76CF" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_770854EC5EE7BFA210E8D99ED1CC5820" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ServiceAgreementsMember" xlink:label="loc_us-gaap_ServiceAgreementsMember_1700154F99CF9A578D3DD99ED1CD3BCE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_770854EC5EE7BFA210E8D99ED1CC5820" xlink:to="loc_us-gaap_ServiceAgreementsMember_1700154F99CF9A578D3DD99ED1CD3BCE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CustomerRelationshipsMember" xlink:label="loc_us-gaap_CustomerRelationshipsMember_568E98B0884AE1B1A201D99ED1CD9B32" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_770854EC5EE7BFA210E8D99ED1CC5820" xlink:to="loc_us-gaap_CustomerRelationshipsMember_568E98B0884AE1B1A201D99ED1CD9B32" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_ResidualBuyoutsMember" xlink:label="loc_prth_ResidualBuyoutsMember_B5F3D450B987217CB27DD99ED1CEC63A" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_770854EC5EE7BFA210E8D99ED1CC5820" xlink:to="loc_prth_ResidualBuyoutsMember_B5F3D450B987217CB27DD99ED1CEC63A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NoncompeteAgreementsMember" xlink:label="loc_us-gaap_NoncompeteAgreementsMember_C5E88DBABD70A1D0659BD99ED1CE47AF" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_770854EC5EE7BFA210E8D99ED1CC5820" xlink:to="loc_us-gaap_NoncompeteAgreementsMember_C5E88DBABD70A1D0659BD99ED1CE47AF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TradeNamesMember" xlink:label="loc_us-gaap_TradeNamesMember_4896B76FF89FDF7A1283D99ED1CE6690" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_770854EC5EE7BFA210E8D99ED1CC5820" xlink:to="loc_us-gaap_TradeNamesMember_4896B76FF89FDF7A1283D99ED1CE6690" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DevelopedTechnologyRightsMember" xlink:label="loc_us-gaap_DevelopedTechnologyRightsMember_8D53AAA821947B543AE5D99ED1CFB176" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_770854EC5EE7BFA210E8D99ED1CC5820" xlink:to="loc_us-gaap_DevelopedTechnologyRightsMember_8D53AAA821947B543AE5D99ED1CFB176" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_ISORelationshipsMember" xlink:label="loc_prth_ISORelationshipsMember_DEBF5132AA04CC1426DDD99ED1D0738B" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_770854EC5EE7BFA210E8D99ED1CC5820" xlink:to="loc_prth_ISORelationshipsMember_DEBF5132AA04CC1426DDD99ED1D0738B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsGross" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_017B8DF05968C5BE600FD99ED1D1CAB6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_273260E50C1C2D2FEC05D99ED1D1B502" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_017B8DF05968C5BE600FD99ED1D1CAB6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_04CF85774D595737389BD99ED1D1948A" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_273260E50C1C2D2FEC05D99ED1D1B502" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_04CF85774D595737389BD99ED1D1948A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsNet" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_B64F40F9EEB64BA6D0DFD99ED1D1BDED" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_273260E50C1C2D2FEC05D99ED1D1B502" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_B64F40F9EEB64BA6D0DFD99ED1D1BDED" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://miacquisitions.com/role/GoodwillAndIntangibleAssetsNarrativeDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://miacquisitions.com/role/GoodwillAndIntangibleAssetsTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://miacquisitions.com/role/IncomeTaxes" xlink:type="extended" />
  <link:definitionLink xlink:role="http://miacquisitions.com/role/IncomeTaxesNarrativeDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://miacquisitions.com/role/IncomeTaxesScheduleOfIncomeTaxBenefitProvisionDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://miacquisitions.com/role/IncomeTaxesTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://miacquisitions.com/role/LossPerCommonShare" xlink:type="extended" />
  <link:definitionLink xlink:role="http://miacquisitions.com/role/LossPerCommonShareScheduleOfAntidilutiveSecuritiesDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_FC9D779A8627C8349E9FE96E415EF08A" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable" xlink:label="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_BC1F34A7AD92AC23AE97E96E415147C0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_FC9D779A8627C8349E9FE96E415EF08A" xlink:to="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_BC1F34A7AD92AC23AE97E96E415147C0" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_D3BC9E1FC7B3E8FD7C49E96E41513C22" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_BC1F34A7AD92AC23AE97E96E415147C0" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_D3BC9E1FC7B3E8FD7C49E96E41513C22" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AntidilutiveSecuritiesNameDomain" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_2CBDF029049938648EF7E96E4152E513_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_D3BC9E1FC7B3E8FD7C49E96E41513C22" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_2CBDF029049938648EF7E96E4152E513_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AntidilutiveSecuritiesNameDomain" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_2CBDF029049938648EF7E96E4152E513" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_D3BC9E1FC7B3E8FD7C49E96E41513C22" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_2CBDF029049938648EF7E96E4152E513" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_WarrantMember" xlink:label="loc_us-gaap_WarrantMember_A611853349D46A0AB222E96E41526C9A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_2CBDF029049938648EF7E96E4152E513" xlink:to="loc_us-gaap_WarrantMember_A611853349D46A0AB222E96E41526C9A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestrictedStockUnitsRSUMember" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_5BEBA27032A8CC0310F5E96E415AE0E4" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_2CBDF029049938648EF7E96E4152E513" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_5BEBA27032A8CC0310F5E96E415AE0E4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EmployeeStockOptionMember" xlink:label="loc_us-gaap_EmployeeStockOptionMember_994B913C04F001D1E2E4E96E415C6A42" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_2CBDF029049938648EF7E96E4152E513" xlink:to="loc_us-gaap_EmployeeStockOptionMember_994B913C04F001D1E2E4E96E415C6A42" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_LiabilityBasedRestrictedStockUnitMember" xlink:label="loc_prth_LiabilityBasedRestrictedStockUnitMember_54FF36F0583AAD5C5B61E96E415D3842" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_2CBDF029049938648EF7E96E4152E513" xlink:to="loc_prth_LiabilityBasedRestrictedStockUnitMember_54FF36F0583AAD5C5B61E96E415D3842" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_EarnoutIncentiveAwardsMember" xlink:label="loc_prth_EarnoutIncentiveAwardsMember_8B5EF4312EE8FEC5FEE1E96E415E7C3E" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_2CBDF029049938648EF7E96E4152E513" xlink:to="loc_prth_EarnoutIncentiveAwardsMember_8B5EF4312EE8FEC5FEE1E96E415E7C3E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_E694E648BE4EC7915D73E96E415E4ED5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_FC9D779A8627C8349E9FE96E415EF08A" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_E694E648BE4EC7915D73E96E415E4ED5" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://miacquisitions.com/role/LossPerCommonShareScheduleOfEarningsPerShareDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://miacquisitions.com/role/LossPerCommonShareTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://miacquisitions.com/role/NonControllingInterests" xlink:type="extended" />
  <link:definitionLink xlink:role="http://miacquisitions.com/role/NonControllingInterestsYapstoneDetails" xlink:type="extended">
    <link:loc xlink:href="prth-20200630.xsd#prth_ScheduleofAssetAcquisitionLineItems" xlink:label="loc_prth_ScheduleofAssetAcquisitionLineItems_BAFDAC0AAD59B5F18981DEBCF3E610CE" xlink:type="locator" />
    <link:loc xlink:href="prth-20200630.xsd#prth_ScheduleofAssetAcquisitionTable" xlink:label="loc_prth_ScheduleofAssetAcquisitionTable_423F8F5FCA3C41A44799DEBCF3E52CDE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_prth_ScheduleofAssetAcquisitionLineItems_BAFDAC0AAD59B5F18981DEBCF3E610CE" xlink:to="loc_prth_ScheduleofAssetAcquisitionTable_423F8F5FCA3C41A44799DEBCF3E52CDE" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="prth-20200630.xsd#prth_AssetAcquisitionAxis" xlink:label="loc_prth_AssetAcquisitionAxis_558855C45903ACB12390DEBCF3E5CB62" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_prth_ScheduleofAssetAcquisitionTable_423F8F5FCA3C41A44799DEBCF3E52CDE" xlink:to="loc_prth_AssetAcquisitionAxis_558855C45903ACB12390DEBCF3E5CB62" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_AssetAcquisitionDomain" xlink:label="loc_prth_AssetAcquisitionDomain_17A75E32EE9DA655D880DEBCF3E60E9C_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_prth_AssetAcquisitionAxis_558855C45903ACB12390DEBCF3E5CB62" xlink:to="loc_prth_AssetAcquisitionDomain_17A75E32EE9DA655D880DEBCF3E60E9C_default" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_AssetAcquisitionDomain" xlink:label="loc_prth_AssetAcquisitionDomain_17A75E32EE9DA655D880DEBCF3E60E9C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_prth_AssetAcquisitionAxis_558855C45903ACB12390DEBCF3E5CB62" xlink:to="loc_prth_AssetAcquisitionDomain_17A75E32EE9DA655D880DEBCF3E60E9C" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_YapStoneIncMember" xlink:label="loc_prth_YapStoneIncMember_CACDD1234085DECE9301DEBCF3E68B06" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_prth_AssetAcquisitionDomain_17A75E32EE9DA655D880DEBCF3E60E9C" xlink:to="loc_prth_YapStoneIncMember_CACDD1234085DECE9301DEBCF3E68B06" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_PaymentsForAssetAcquisitions" xlink:label="loc_prth_PaymentsForAssetAcquisitions_92F5DBE6EAF07096479DDEBCF3E7E345" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_prth_ScheduleofAssetAcquisitionLineItems_BAFDAC0AAD59B5F18981DEBCF3E610CE" xlink:to="loc_prth_PaymentsForAssetAcquisitions_92F5DBE6EAF07096479DDEBCF3E7E345" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MinorityInterest" xlink:label="loc_us-gaap_MinorityInterest_EECD1D05A506B4D69E32DEBCF3E74B8E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_prth_ScheduleofAssetAcquisitionLineItems_BAFDAC0AAD59B5F18981DEBCF3E610CE" xlink:to="loc_us-gaap_MinorityInterest_EECD1D05A506B4D69E32DEBCF3E74B8E" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_AssetAcquisitionSoftwareLicenseAgreement" xlink:label="loc_prth_AssetAcquisitionSoftwareLicenseAgreement_E1A6DE95DD0D2AEC09EFDEBCF3E7B03C" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_prth_ScheduleofAssetAcquisitionLineItems_BAFDAC0AAD59B5F18981DEBCF3E610CE" xlink:to="loc_prth_AssetAcquisitionSoftwareLicenseAgreement_E1A6DE95DD0D2AEC09EFDEBCF3E7B03C" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_AssetAcquisitionServiceAgreement" xlink:label="loc_prth_AssetAcquisitionServiceAgreement_CE00211435C0A92715E1DEBCF3E85A26" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_prth_ScheduleofAssetAcquisitionLineItems_BAFDAC0AAD59B5F18981DEBCF3E610CE" xlink:to="loc_prth_AssetAcquisitionServiceAgreement_CE00211435C0A92715E1DEBCF3E85A26" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://miacquisitions.com/role/PropertyEquipmentAndSoftware" xlink:type="extended" />
  <link:definitionLink xlink:role="http://miacquisitions.com/role/PropertyEquipmentAndSoftwareNarrativeAndScheduleOfPropertyEquipmentAndSoftwareDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PropertyPlantAndEquipmentLineItems" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_A8E72C8BBF2CE1F56DC3D99ED14D5EDF" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_AA36ED77DF2750B0D01AD99ED13D89C4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_A8E72C8BBF2CE1F56DC3D99ED14D5EDF" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_AA36ED77DF2750B0D01AD99ED13D89C4" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_12F12E758244ACC627CBD99ED13E7242" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_AA36ED77DF2750B0D01AD99ED13D89C4" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_12F12E758244ACC627CBD99ED13E7242" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_D7219EE56AF685672610D99ED1413539_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_12F12E758244ACC627CBD99ED13E7242" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_D7219EE56AF685672610D99ED1413539_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_D7219EE56AF685672610D99ED1413539" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_12F12E758244ACC627CBD99ED13E7242" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_D7219EE56AF685672610D99ED1413539" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FurnitureAndFixturesMember" xlink:label="loc_us-gaap_FurnitureAndFixturesMember_8159D2E26084B14909F5D99ED145F5EE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_D7219EE56AF685672610D99ED1413539" xlink:to="loc_us-gaap_FurnitureAndFixturesMember_8159D2E26084B14909F5D99ED145F5EE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EquipmentMember" xlink:label="loc_us-gaap_EquipmentMember_2CEF80CD9F215C6977A0D99ED14511C3" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_D7219EE56AF685672610D99ED1413539" xlink:to="loc_us-gaap_EquipmentMember_2CEF80CD9F215C6977A0D99ED14511C3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SoftwareAndSoftwareDevelopmentCostsMember" xlink:label="loc_us-gaap_SoftwareAndSoftwareDevelopmentCostsMember_39C7FADE26AC237BF155D99ED146C244" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_D7219EE56AF685672610D99ED1413539" xlink:to="loc_us-gaap_SoftwareAndSoftwareDevelopmentCostsMember_39C7FADE26AC237BF155D99ED146C244" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LeaseholdImprovementsMember" xlink:label="loc_us-gaap_LeaseholdImprovementsMember_3C0328A35F4BCDD567F5D99ED1470FDD" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_D7219EE56AF685672610D99ED1413539" xlink:to="loc_us-gaap_LeaseholdImprovementsMember_3C0328A35F4BCDD567F5D99ED1470FDD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeAxis" xlink:label="loc_srt_RangeAxis_524DAD1FC1DF0306A712D99ED1476B60" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_AA36ED77DF2750B0D01AD99ED13D89C4" xlink:to="loc_srt_RangeAxis_524DAD1FC1DF0306A712D99ED1476B60" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_4D76ED852B14C202AB3BD99ED14899C8_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_524DAD1FC1DF0306A712D99ED1476B60" xlink:to="loc_srt_RangeMember_4D76ED852B14C202AB3BD99ED14899C8_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_4D76ED852B14C202AB3BD99ED14899C8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_524DAD1FC1DF0306A712D99ED1476B60" xlink:to="loc_srt_RangeMember_4D76ED852B14C202AB3BD99ED14899C8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_MinimumMember" xlink:label="loc_srt_MinimumMember_C0C31266FFC3F5E12760D99ED14BDE81" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_4D76ED852B14C202AB3BD99ED14899C8" xlink:to="loc_srt_MinimumMember_C0C31266FFC3F5E12760D99ED14BDE81" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_MaximumMember" xlink:label="loc_srt_MaximumMember_177387E91F6636590520D99ED14BA0BD" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_4D76ED852B14C202AB3BD99ED14899C8" xlink:to="loc_srt_MaximumMember_177387E91F6636590520D99ED14BA0BD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PropertyPlantAndEquipmentGross" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentGross_1420BB22E0D28956AB4BD99ED14D33A3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_A8E72C8BBF2CE1F56DC3D99ED14D5EDF" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentGross_1420BB22E0D28956AB4BD99ED14D33A3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment" xlink:label="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_87B6D7A50B0CE99B5A6AD99ED150EABB" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_A8E72C8BBF2CE1F56DC3D99ED14D5EDF" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_87B6D7A50B0CE99B5A6AD99ED150EABB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_7EEAB25E812A115C66A6D99ED1501ACA" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_A8E72C8BBF2CE1F56DC3D99ED14D5EDF" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_7EEAB25E812A115C66A6D99ED1501ACA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PropertyPlantAndEquipmentUsefulLife" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentUsefulLife_94900A695BDF292307A7D99ED15043E2" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_A8E72C8BBF2CE1F56DC3D99ED14D5EDF" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentUsefulLife_94900A695BDF292307A7D99ED15043E2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_Depreciation" xlink:label="loc_us-gaap_Depreciation_E3ED646A113BF701022FD99ED151F18A" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_A8E72C8BBF2CE1F56DC3D99ED14D5EDF" xlink:to="loc_us-gaap_Depreciation_E3ED646A113BF701022FD99ED151F18A" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://miacquisitions.com/role/PropertyEquipmentAndSoftwareTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://miacquisitions.com/role/ReconciliationOfStockholdersDeficitAndNonControllingInterest" xlink:type="extended" />
  <link:definitionLink xlink:role="http://miacquisitions.com/role/ReconciliationOfStockholdersDeficitAndNonControllingInterestEquityReconciliationDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ClassOfStockLineItems" xlink:label="loc_us-gaap_ClassOfStockLineItems_2192F8D9A782B1A4EF75E96D67911F39" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfStockByClassTable" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_17B0F6B7E6BE761B274EE96D6785820E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_2192F8D9A782B1A4EF75E96D67911F39" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_17B0F6B7E6BE761B274EE96D6785820E" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ClassOfWarrantOrRightAxis" xlink:label="loc_us-gaap_ClassOfWarrantOrRightAxis_8145535D6CD2EF04DE29E96D6786ADD3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_17B0F6B7E6BE761B274EE96D6785820E" xlink:to="loc_us-gaap_ClassOfWarrantOrRightAxis_8145535D6CD2EF04DE29E96D6786ADD3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ClassOfWarrantOrRightDomain" xlink:label="loc_us-gaap_ClassOfWarrantOrRightDomain_4FE200450518B7180032E96D678731E5_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_8145535D6CD2EF04DE29E96D6786ADD3" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_4FE200450518B7180032E96D678731E5_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ClassOfWarrantOrRightDomain" xlink:label="loc_us-gaap_ClassOfWarrantOrRightDomain_4FE200450518B7180032E96D678731E5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_8145535D6CD2EF04DE29E96D6786ADD3" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_4FE200450518B7180032E96D678731E5" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_MIAcquisitionsWarrantsPublicMember" xlink:label="loc_prth_MIAcquisitionsWarrantsPublicMember_383CAED3FA6F7F7E1E79E96D67871E8C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightDomain_4FE200450518B7180032E96D678731E5" xlink:to="loc_prth_MIAcquisitionsWarrantsPublicMember_383CAED3FA6F7F7E1E79E96D67871E8C" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_MIAcquisitionsWarrantsPrivateMember" xlink:label="loc_prth_MIAcquisitionsWarrantsPrivateMember_ED1B9557EA3ABD982F06E96D6788DFE9" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightDomain_4FE200450518B7180032E96D678731E5" xlink:to="loc_prth_MIAcquisitionsWarrantsPrivateMember_ED1B9557EA3ABD982F06E96D6788DFE9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_DE3D9438DDDB615A4AC7E96D678A59D4" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_17B0F6B7E6BE761B274EE96D6785820E" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_DE3D9438DDDB615A4AC7E96D678A59D4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_5A6E37B2C2F5594AA5A6E96D678A6A82_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_DE3D9438DDDB615A4AC7E96D678A59D4" xlink:to="loc_us-gaap_EquityComponentDomain_5A6E37B2C2F5594AA5A6E96D678A6A82_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_5A6E37B2C2F5594AA5A6E96D678A6A82" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_DE3D9438DDDB615A4AC7E96D678A59D4" xlink:to="loc_us-gaap_EquityComponentDomain_5A6E37B2C2F5594AA5A6E96D678A6A82" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PreferredStockMember" xlink:label="loc_us-gaap_PreferredStockMember_DFD62EDD7F489D1BD5D3E96D678B94F2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_5A6E37B2C2F5594AA5A6E96D678A6A82" xlink:to="loc_us-gaap_PreferredStockMember_DFD62EDD7F489D1BD5D3E96D678B94F2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonStockMember" xlink:label="loc_us-gaap_CommonStockMember_2E9C2244BBE521DBB210E96D678FCEA2" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_5A6E37B2C2F5594AA5A6E96D678A6A82" xlink:to="loc_us-gaap_CommonStockMember_2E9C2244BBE521DBB210E96D678FCEA2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TreasuryStockMember" xlink:label="loc_us-gaap_TreasuryStockMember_86EAA6EBE1CC47292892E96D67908570" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_5A6E37B2C2F5594AA5A6E96D678A6A82" xlink:to="loc_us-gaap_TreasuryStockMember_86EAA6EBE1CC47292892E96D67908570" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AdditionalPaidInCapitalMember" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_359433A3857A7BD6A612E96D6790ABAB" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_5A6E37B2C2F5594AA5A6E96D678A6A82" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_359433A3857A7BD6A612E96D6790ABAB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetainedEarningsMember" xlink:label="loc_us-gaap_RetainedEarningsMember_1EE059EDCC326E118559E96D67905564" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_5A6E37B2C2F5594AA5A6E96D678A6A82" xlink:to="loc_us-gaap_RetainedEarningsMember_1EE059EDCC326E118559E96D67905564" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ParentMember" xlink:label="loc_us-gaap_ParentMember_E6029127D07425787CC1E96D67909B03" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_5A6E37B2C2F5594AA5A6E96D678A6A82" xlink:to="loc_us-gaap_ParentMember_E6029127D07425787CC1E96D67909B03" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NoncontrollingInterestMember" xlink:label="loc_us-gaap_NoncontrollingInterestMember_C641167AB736C967657EE96D6790EB29" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_5A6E37B2C2F5594AA5A6E96D678A6A82" xlink:to="loc_us-gaap_NoncontrollingInterestMember_C641167AB736C967657EE96D6790EB29" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_BBCEF49BDEF1E310D098E96D679183B0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_2192F8D9A782B1A4EF75E96D67911F39" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_BBCEF49BDEF1E310D098E96D679183B0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SharesOutstanding" xlink:label="loc_us-gaap_SharesOutstanding_7B5F25925CD109537BDEE96D67910868" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_BBCEF49BDEF1E310D098E96D679183B0" xlink:to="loc_us-gaap_SharesOutstanding_7B5F25925CD109537BDEE96D67910868" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_DFBAFC3A0BA93D580423E96D6791D473" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_BBCEF49BDEF1E310D098E96D679183B0" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_DFBAFC3A0BA93D580423E96D6791D473" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_3F65AB6CF12F8B0E9F4BE96D67921CD4" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_BBCEF49BDEF1E310D098E96D679183B0" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_3F65AB6CF12F8B0E9F4BE96D67921CD4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockRepurchasedDuringPeriodShares" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodShares_07B97DA4E8887F611186E96D67922ACA" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_BBCEF49BDEF1E310D098E96D679183B0" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodShares_07B97DA4E8887F611186E96D67922ACA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockRepurchasedDuringPeriodValue" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodValue_83C9724B9F3712850F50E96D6793747B" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_BBCEF49BDEF1E310D098E96D679183B0" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodValue_83C9724B9F3712850F50E96D6793747B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities_2C1258FF4A67DDCC45EEE96D679366FD" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_BBCEF49BDEF1E310D098E96D679183B0" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities_2C1258FF4A67DDCC45EEE96D679366FD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="loc_us-gaap_NetIncomeLoss_E026C0F504FF5C496586E96D6793C29E" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_BBCEF49BDEF1E310D098E96D679183B0" xlink:to="loc_us-gaap_NetIncomeLoss_E026C0F504FF5C496586E96D6793C29E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NoncontrollingInterestIncreaseFromSubsidiaryEquityIssuance" xlink:label="loc_us-gaap_NoncontrollingInterestIncreaseFromSubsidiaryEquityIssuance_10E34A048E4508955303E96D6793DA5F" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_BBCEF49BDEF1E310D098E96D679183B0" xlink:to="loc_us-gaap_NoncontrollingInterestIncreaseFromSubsidiaryEquityIssuance_10E34A048E4508955303E96D6793DA5F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities_CE4A748EB57488357E30E96D67943989" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_2192F8D9A782B1A4EF75E96D67911F39" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities_CE4A748EB57488357E30E96D67943989" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ClassOfWarrantOrRightOutstanding" xlink:label="loc_us-gaap_ClassOfWarrantOrRightOutstanding_40CD3B283D59CF2E74FDE96D67945EF4" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_2192F8D9A782B1A4EF75E96D67911F39" xlink:to="loc_us-gaap_ClassOfWarrantOrRightOutstanding_40CD3B283D59CF2E74FDE96D67945EF4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights" xlink:label="loc_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_5B047686C9D66D413068E96D67953802" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_2192F8D9A782B1A4EF75E96D67911F39" xlink:to="loc_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_5B047686C9D66D413068E96D67953802" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight" xlink:label="loc_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight_4BDC97DDCA0253AD503DE96D67951C96" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_2192F8D9A782B1A4EF75E96D67911F39" xlink:to="loc_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight_4BDC97DDCA0253AD503DE96D67951C96" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NetIncomeLossAttributableToNoncontrollingInterest" xlink:label="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_02AAEF68C32772F81068E96D6795D30A" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_2192F8D9A782B1A4EF75E96D67911F39" xlink:to="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_02AAEF68C32772F81068E96D6795D30A" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://miacquisitions.com/role/ReconciliationOfStockholdersDeficitAndNonControllingInterestNarrativeDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://miacquisitions.com/role/ReconciliationOfStockholdersDeficitAndNonControllingInterestTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://miacquisitions.com/role/RelatedPartyTransactions" xlink:type="extended" />
  <link:definitionLink xlink:role="http://miacquisitions.com/role/RelatedPartyTransactionsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RelatedPartyTransactionLineItems" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_D1000246F16610FA87E2D99ECC38F125" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_880B38FEC2CA34B3A444D99ECC2F9FFC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_D1000246F16610FA87E2D99ECC38F125" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_880B38FEC2CA34B3A444D99ECC2F9FFC" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_LegalEntityAxis" xlink:label="loc_dei_LegalEntityAxis_FB8493BD30C4DDA96127D99ECC30C714" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_880B38FEC2CA34B3A444D99ECC2F9FFC" xlink:to="loc_dei_LegalEntityAxis_FB8493BD30C4DDA96127D99ECC30C714" xlink:type="arc" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain" xlink:label="loc_dei_EntityDomain_010C61A29F11F2373867D99ECC33CD64_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_FB8493BD30C4DDA96127D99ECC30C714" xlink:to="loc_dei_EntityDomain_010C61A29F11F2373867D99ECC33CD64_default" xlink:type="arc" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain" xlink:label="loc_dei_EntityDomain_010C61A29F11F2373867D99ECC33CD64" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_FB8493BD30C4DDA96127D99ECC30C714" xlink:to="loc_dei_EntityDomain_010C61A29F11F2373867D99ECC33CD64" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_PriorityHospitalityTechnologyLLCMember" xlink:label="loc_prth_PriorityHospitalityTechnologyLLCMember_02E94FEA7B57BC0771E8D99ECC343627" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_010C61A29F11F2373867D99ECC33CD64" xlink:to="loc_prth_PriorityHospitalityTechnologyLLCMember_02E94FEA7B57BC0771E8D99ECC343627" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_0D79317174321999AE32D99ECC35A18D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_880B38FEC2CA34B3A444D99ECC2F9FFC" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_0D79317174321999AE32D99ECC35A18D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_C175F1C7D1F5DF6335C9D99ECC3609F2_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_0D79317174321999AE32D99ECC35A18D" xlink:to="loc_us-gaap_RelatedPartyDomain_C175F1C7D1F5DF6335C9D99ECC3609F2_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_C175F1C7D1F5DF6335C9D99ECC3609F2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_0D79317174321999AE32D99ECC35A18D" xlink:to="loc_us-gaap_RelatedPartyDomain_C175F1C7D1F5DF6335C9D99ECC3609F2" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_ChiefExecutiveOfficerAndChairmanMember" xlink:label="loc_prth_ChiefExecutiveOfficerAndChairmanMember_92222076590D885799B4D99ECC36888F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_C175F1C7D1F5DF6335C9D99ECC3609F2" xlink:to="loc_prth_ChiefExecutiveOfficerAndChairmanMember_92222076590D885799B4D99ECC36888F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NotesAndLoansReceivableGrossNoncurrent" xlink:label="loc_us-gaap_NotesAndLoansReceivableGrossNoncurrent_CD7B358F3C0FA470797FD99ECC389A53" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_D1000246F16610FA87E2D99ECC38F125" xlink:to="loc_us-gaap_NotesAndLoansReceivableGrossNoncurrent_CD7B358F3C0FA470797FD99ECC389A53" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_NotesLoansAndFinancingReceivableGrossMaximumLoanCommitmentAvailableForFutureIssuanceNoncurrent" xlink:label="loc_prth_NotesLoansAndFinancingReceivableGrossMaximumLoanCommitmentAvailableForFutureIssuanceNoncurrent_43E932A30C123FA70D02D99ECC3B0FEA" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_D1000246F16610FA87E2D99ECC38F125" xlink:to="loc_prth_NotesLoansAndFinancingReceivableGrossMaximumLoanCommitmentAvailableForFutureIssuanceNoncurrent_43E932A30C123FA70D02D99ECC3B0FEA" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_NotesLoansAndFinancingReceivableGrossNoncurrentAnnualInterestRate" xlink:label="loc_prth_NotesLoansAndFinancingReceivableGrossNoncurrentAnnualInterestRate_BE4086E81E04D90F39F8D99ECC3C3DE2" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_D1000246F16610FA87E2D99ECC38F125" xlink:to="loc_prth_NotesLoansAndFinancingReceivableGrossNoncurrentAnnualInterestRate_BE4086E81E04D90F39F8D99ECC3C3DE2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestIncomeRelatedParty" xlink:label="loc_us-gaap_InterestIncomeRelatedParty_36C622159522B8F1C859D99ECC3F6C95" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_D1000246F16610FA87E2D99ECC38F125" xlink:to="loc_us-gaap_InterestIncomeRelatedParty_36C622159522B8F1C859D99ECC3F6C95" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_PercentageOfOwnershipBeforeTransaction" xlink:label="loc_prth_PercentageOfOwnershipBeforeTransaction_158358A804F52A3BCB0DD99ECC3F836E" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_D1000246F16610FA87E2D99ECC38F125" xlink:to="loc_prth_PercentageOfOwnershipBeforeTransaction_158358A804F52A3BCB0DD99ECC3F836E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RedeemableNoncontrollingInterestEquityPreferredRedemptionValue" xlink:label="loc_us-gaap_RedeemableNoncontrollingInterestEquityPreferredRedemptionValue_47642880B9364064B476D99ECC4046ED" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_D1000246F16610FA87E2D99ECC38F125" xlink:to="loc_us-gaap_RedeemableNoncontrollingInterestEquityPreferredRedemptionValue_47642880B9364064B476D99ECC4046ED" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_RedeemableNoncontrollingInterestEquityPreferredAnnualPreferredYieldPercent" xlink:label="loc_prth_RedeemableNoncontrollingInterestEquityPreferredAnnualPreferredYieldPercent_20D0FAE8A20E7F19B034D99ECC4110E9" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_D1000246F16610FA87E2D99ECC38F125" xlink:to="loc_prth_RedeemableNoncontrollingInterestEquityPreferredAnnualPreferredYieldPercent_20D0FAE8A20E7F19B034D99ECC4110E9" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_PreferredStockPercentageOwned" xlink:label="loc_prth_PreferredStockPercentageOwned_E3D1BEE360D0FD5B7092D99ECC416F8C" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_D1000246F16610FA87E2D99ECC38F125" xlink:to="loc_prth_PreferredStockPercentageOwned_E3D1BEE360D0FD5B7092D99ECC416F8C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NetIncomeLossAttributableToNoncontrollingInterest" xlink:label="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_890AF2A5BE5E10F9CFE6D99ECC4221C3" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_D1000246F16610FA87E2D99ECC38F125" xlink:to="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_890AF2A5BE5E10F9CFE6D99ECC4221C3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeLossFromEquityMethodInvestments" xlink:label="loc_us-gaap_IncomeLossFromEquityMethodInvestments_4ABA24795904FA8766BCD99ECC42D1CB" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_D1000246F16610FA87E2D99ECC38F125" xlink:to="loc_us-gaap_IncomeLossFromEquityMethodInvestments_4ABA24795904FA8766BCD99ECC42D1CB" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://miacquisitions.com/role/Revenues" xlink:type="extended" />
  <link:definitionLink xlink:role="http://miacquisitions.com/role/RevenuesBalanceSheetInformationDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://miacquisitions.com/role/RevenuesDisaggregationOfRevenueDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DisaggregationOfRevenueLineItems" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_E7DA56EF090DA5C3E3F2DE349C52709B" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DisaggregationOfRevenueTable" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_D08D64BFCA2F3D3C6D15DE349C501BDE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_E7DA56EF090DA5C3E3F2DE349C52709B" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_D08D64BFCA2F3D3C6D15DE349C501BDE" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ProductOrServiceAxis" xlink:label="loc_srt_ProductOrServiceAxis_DEB10BD351F545C232F1DE349C51B4A8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_D08D64BFCA2F3D3C6D15DE349C501BDE" xlink:to="loc_srt_ProductOrServiceAxis_DEB10BD351F545C232F1DE349C51B4A8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ProductsAndServicesDomain" xlink:label="loc_srt_ProductsAndServicesDomain_70ABDF9E6F99450CBF51DE349C51C08B_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_DEB10BD351F545C232F1DE349C51B4A8" xlink:to="loc_srt_ProductsAndServicesDomain_70ABDF9E6F99450CBF51DE349C51C08B_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ProductsAndServicesDomain" xlink:label="loc_srt_ProductsAndServicesDomain_70ABDF9E6F99450CBF51DE349C51C08B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_DEB10BD351F545C232F1DE349C51B4A8" xlink:to="loc_srt_ProductsAndServicesDomain_70ABDF9E6F99450CBF51DE349C51C08B" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_MerchantCardFeesMember" xlink:label="loc_prth_MerchantCardFeesMember_6B71A84C9AF56D5B77C3DE349C52BE63" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_70ABDF9E6F99450CBF51DE349C51C08B" xlink:to="loc_prth_MerchantCardFeesMember_6B71A84C9AF56D5B77C3DE349C52BE63" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_OutsourcedServicesAndOtherServicesMember" xlink:label="loc_prth_OutsourcedServicesAndOtherServicesMember_9EA84C2DD114793ED389DE53870429C7" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_70ABDF9E6F99450CBF51DE349C51C08B" xlink:to="loc_prth_OutsourcedServicesAndOtherServicesMember_9EA84C2DD114793ED389DE53870429C7" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_EquipmentSalesMember" xlink:label="loc_prth_EquipmentSalesMember_87A22B8670AB8BFB13D1DE349C52DC4B" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_70ABDF9E6F99450CBF51DE349C51C08B" xlink:to="loc_prth_EquipmentSalesMember_87A22B8670AB8BFB13D1DE349C52DC4B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_0B5D49774C1A9AEA0771DE349C53E3C6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_E7DA56EF090DA5C3E3F2DE349C52709B" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_0B5D49774C1A9AEA0771DE349C53E3C6" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://miacquisitions.com/role/RevenuesNarrativeDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://miacquisitions.com/role/RevenuesTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://miacquisitions.com/role/SegmentInformation" xlink:type="extended" />
  <link:definitionLink xlink:role="http://miacquisitions.com/role/SegmentInformationNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentReportingInformationLineItems" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_D74B6FC450BD2915D31CD99EC9B1500B" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_81DDF23E2E51D3176105D99EC9AEA2BD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_D74B6FC450BD2915D31CD99EC9B1500B" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_81DDF23E2E51D3176105D99EC9AEA2BD" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_5DB3BF4C0A5475CD7548D99EC9AF7EEE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_81DDF23E2E51D3176105D99EC9AEA2BD" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_5DB3BF4C0A5475CD7548D99EC9AF7EEE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_4752D5295F4D92E0DA7AD99EC9AF668A_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_5DB3BF4C0A5475CD7548D99EC9AF7EEE" xlink:to="loc_us-gaap_SegmentDomain_4752D5295F4D92E0DA7AD99EC9AF668A_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_4752D5295F4D92E0DA7AD99EC9AF668A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_5DB3BF4C0A5475CD7548D99EC9AF7EEE" xlink:to="loc_us-gaap_SegmentDomain_4752D5295F4D92E0DA7AD99EC9AF668A" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_CommercialPaymentsAndManagedServicesMember" xlink:label="loc_prth_CommercialPaymentsAndManagedServicesMember_E9E1E7AC722D750B46A2D99EC9B1F3BF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_4752D5295F4D92E0DA7AD99EC9AF668A" xlink:to="loc_prth_CommercialPaymentsAndManagedServicesMember_E9E1E7AC722D750B46A2D99EC9B1F3BF" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_ConsumerPaymentsMember" xlink:label="loc_prth_ConsumerPaymentsMember_9E059B0CF538F43A7E0FD99EC9B1951A" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_4752D5295F4D92E0DA7AD99EC9AF668A" xlink:to="loc_prth_ConsumerPaymentsMember_9E059B0CF538F43A7E0FD99EC9B1951A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NumberOfReportableSegments" xlink:label="loc_us-gaap_NumberOfReportableSegments_DC61BD61F63A3891887DD99EC9B1D0F8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_D74B6FC450BD2915D31CD99EC9B1500B" xlink:to="loc_us-gaap_NumberOfReportableSegments_DC61BD61F63A3891887DD99EC9B1D0F8" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_PercentageofRevenue" xlink:label="loc_prth_PercentageofRevenue_F17E9C350ADBA3998ED5D99EC9B2CBFB" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_D74B6FC450BD2915D31CD99EC9B1500B" xlink:to="loc_prth_PercentageofRevenue_F17E9C350ADBA3998ED5D99EC9B2CBFB" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://miacquisitions.com/role/SegmentInformationScheduleOfReconciliationOfTotalOperatingIncomeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentReportingInformationLineItems" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_62A03A4783BAED7727A6DE349A4140EB" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_F72F7A9E5BC31CA91791DE349A40004D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_62A03A4783BAED7727A6DE349A4140EB" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_F72F7A9E5BC31CA91791DE349A40004D" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ConsolidationItemsAxis" xlink:label="loc_srt_ConsolidationItemsAxis_654592C9B05285C74669DE349A408BA6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_F72F7A9E5BC31CA91791DE349A40004D" xlink:to="loc_srt_ConsolidationItemsAxis_654592C9B05285C74669DE349A408BA6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ConsolidationItemsDomain" xlink:label="loc_srt_ConsolidationItemsDomain_7C8523D0CF63A5EE483BDE349A401BC9_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_654592C9B05285C74669DE349A408BA6" xlink:to="loc_srt_ConsolidationItemsDomain_7C8523D0CF63A5EE483BDE349A401BC9_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ConsolidationItemsDomain" xlink:label="loc_srt_ConsolidationItemsDomain_7C8523D0CF63A5EE483BDE349A401BC9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_654592C9B05285C74669DE349A408BA6" xlink:to="loc_srt_ConsolidationItemsDomain_7C8523D0CF63A5EE483BDE349A401BC9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingSegmentsMember" xlink:label="loc_us-gaap_OperatingSegmentsMember_F374C0598DB232A29AF4DE349A416116" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_7C8523D0CF63A5EE483BDE349A401BC9" xlink:to="loc_us-gaap_OperatingSegmentsMember_F374C0598DB232A29AF4DE349A416116" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CorporateNonSegmentMember" xlink:label="loc_us-gaap_CorporateNonSegmentMember_E5C6C0FCCCC067A5E878DE349A41FD19" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_7C8523D0CF63A5EE483BDE349A401BC9" xlink:to="loc_us-gaap_CorporateNonSegmentMember_E5C6C0FCCCC067A5E878DE349A41FD19" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingIncomeLoss" xlink:label="loc_us-gaap_OperatingIncomeLoss_EFC89B51BAB7BF197882DE349A41923C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_62A03A4783BAED7727A6DE349A4140EB" xlink:to="loc_us-gaap_OperatingIncomeLoss_EFC89B51BAB7BF197882DE349A41923C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestExpense" xlink:label="loc_us-gaap_InterestExpense_F51D501D90C577A563A0DE349A42A9B4" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_62A03A4783BAED7727A6DE349A4140EB" xlink:to="loc_us-gaap_InterestExpense_F51D501D90C577A563A0DE349A42A9B4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherNonoperatingIncomeExpense" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_17F1422B25690B1E3C8BDE349A42BB2E" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_62A03A4783BAED7727A6DE349A4140EB" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_17F1422B25690B1E3C8BDE349A42BB2E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeTaxExpenseBenefit" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_BD11E825556067F8191ADE349A431040" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_62A03A4783BAED7727A6DE349A4140EB" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_BD11E825556067F8191ADE349A431040" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="loc_us-gaap_NetIncomeLoss_76BACB53F341C6387D9DDE349A4372CC" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_62A03A4783BAED7727A6DE349A4140EB" xlink:to="loc_us-gaap_NetIncomeLoss_76BACB53F341C6387D9DDE349A4372CC" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://miacquisitions.com/role/SegmentInformationScheduleOfSegmentReportingInformationBySegmentDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentReportingInformationLineItems" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_E8AEBB2206856EBEC409D99EC98098A0" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_C9CFBD10E4276B9EB7B0D99EC9737841" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_E8AEBB2206856EBEC409D99EC98098A0" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_C9CFBD10E4276B9EB7B0D99EC9737841" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ConsolidationItemsAxis" xlink:label="loc_srt_ConsolidationItemsAxis_22AD6A55C0D163EC1047D99EC976E387" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_C9CFBD10E4276B9EB7B0D99EC9737841" xlink:to="loc_srt_ConsolidationItemsAxis_22AD6A55C0D163EC1047D99EC976E387" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ConsolidationItemsDomain" xlink:label="loc_srt_ConsolidationItemsDomain_EB4C81F5828834519DC6D99EC977EF8A_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_22AD6A55C0D163EC1047D99EC976E387" xlink:to="loc_srt_ConsolidationItemsDomain_EB4C81F5828834519DC6D99EC977EF8A_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ConsolidationItemsDomain" xlink:label="loc_srt_ConsolidationItemsDomain_EB4C81F5828834519DC6D99EC977EF8A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_22AD6A55C0D163EC1047D99EC976E387" xlink:to="loc_srt_ConsolidationItemsDomain_EB4C81F5828834519DC6D99EC977EF8A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingSegmentsMember" xlink:label="loc_us-gaap_OperatingSegmentsMember_605B0BC8C41ADA74E811D99EC97A19B7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_EB4C81F5828834519DC6D99EC977EF8A" xlink:to="loc_us-gaap_OperatingSegmentsMember_605B0BC8C41ADA74E811D99EC97A19B7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CorporateNonSegmentMember" xlink:label="loc_us-gaap_CorporateNonSegmentMember_B7D2A81CAC41B2E5551DD99EC97B97EE" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_EB4C81F5828834519DC6D99EC977EF8A" xlink:to="loc_us-gaap_CorporateNonSegmentMember_B7D2A81CAC41B2E5551DD99EC97B97EE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_493B5D415BFBCD8283F5D99EC97DFBBA" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_C9CFBD10E4276B9EB7B0D99EC9737841" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_493B5D415BFBCD8283F5D99EC97DFBBA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_8AEEABD777ACB23F7D3CD99EC97D2D7A_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_493B5D415BFBCD8283F5D99EC97DFBBA" xlink:to="loc_us-gaap_SegmentDomain_8AEEABD777ACB23F7D3CD99EC97D2D7A_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_8AEEABD777ACB23F7D3CD99EC97D2D7A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_493B5D415BFBCD8283F5D99EC97DFBBA" xlink:to="loc_us-gaap_SegmentDomain_8AEEABD777ACB23F7D3CD99EC97D2D7A" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_ConsumerPaymentsMember" xlink:label="loc_prth_ConsumerPaymentsMember_D5230F6FF8100CDAF497D99EC97E3294" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_8AEEABD777ACB23F7D3CD99EC97D2D7A" xlink:to="loc_prth_ConsumerPaymentsMember_D5230F6FF8100CDAF497D99EC97E3294" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_CommercialPaymentsAndManagedServicesMember" xlink:label="loc_prth_CommercialPaymentsAndManagedServicesMember_837A5B463446E3D9A70DD99EC97F7632" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_8AEEABD777ACB23F7D3CD99EC97D2D7A" xlink:to="loc_prth_CommercialPaymentsAndManagedServicesMember_837A5B463446E3D9A70DD99EC97F7632" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_IntegratedPartnersMember" xlink:label="loc_prth_IntegratedPartnersMember_1E3551A53040E421189FD99EC97F1BA3" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_8AEEABD777ACB23F7D3CD99EC97D2D7A" xlink:to="loc_prth_IntegratedPartnersMember_1E3551A53040E421189FD99EC97F1BA3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevenuesAbstract" xlink:label="loc_us-gaap_RevenuesAbstract_F2707CF7FBD04E433BB2D99EC980B995" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_E8AEBB2206856EBEC409D99EC98098A0" xlink:to="loc_us-gaap_RevenuesAbstract_F2707CF7FBD04E433BB2D99EC980B995" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_DD2F5E2E0F1FE0FF1BE6D99EC981564D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_F2707CF7FBD04E433BB2D99EC980B995" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_DD2F5E2E0F1FE0FF1BE6D99EC981564D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NetIncomeLossAbstract" xlink:label="loc_us-gaap_NetIncomeLossAbstract_60B756A8C9DD0BB738E4D99EC981D0EC" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_E8AEBB2206856EBEC409D99EC98098A0" xlink:to="loc_us-gaap_NetIncomeLossAbstract_60B756A8C9DD0BB738E4D99EC981D0EC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingIncomeLoss" xlink:label="loc_us-gaap_OperatingIncomeLoss_F7C9CA82839FD861E96DD99EC981311C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetIncomeLossAbstract_60B756A8C9DD0BB738E4D99EC981D0EC" xlink:to="loc_us-gaap_OperatingIncomeLoss_F7C9CA82839FD861E96DD99EC981311C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DepreciationAmortizationAndAccretionNetAbstract" xlink:label="loc_us-gaap_DepreciationAmortizationAndAccretionNetAbstract_EE1DCFFCAF0E587D27FED99EC9823DAB" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_E8AEBB2206856EBEC409D99EC98098A0" xlink:to="loc_us-gaap_DepreciationAmortizationAndAccretionNetAbstract_EE1DCFFCAF0E587D27FED99EC9823DAB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DepreciationAndAmortization" xlink:label="loc_us-gaap_DepreciationAndAmortization_E23F44E4CC079775F476D99EC98A28B2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DepreciationAmortizationAndAccretionNetAbstract_EE1DCFFCAF0E587D27FED99EC9823DAB" xlink:to="loc_us-gaap_DepreciationAndAmortization_E23F44E4CC079775F476D99EC98A28B2" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://miacquisitions.com/role/SegmentInformationTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://miacquisitions.com/role/SettlementAssetsAndObligations" xlink:type="extended" />
  <link:definitionLink xlink:role="http://miacquisitions.com/role/SettlementAssetsAndObligationsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccountsNotesAndLoansReceivableLineItems" xlink:label="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_3497D1DCD2F4A3FE7FEDD99ED34EF203" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable" xlink:label="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_CD8DE929CD3AB1E11A9DD99ED33064FB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_3497D1DCD2F4A3FE7FEDD99ED34EF203" xlink:to="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_CD8DE929CD3AB1E11A9DD99ED33064FB" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis" xlink:label="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_ABFE27E23330883965D2D99ED3319DAB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_CD8DE929CD3AB1E11A9DD99ED33064FB" xlink:to="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_ABFE27E23330883965D2D99ED3319DAB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ReceivableTypeDomain" xlink:label="loc_us-gaap_ReceivableTypeDomain_CAEFC554FD669DC9478BD99ED3341B86_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_ABFE27E23330883965D2D99ED3319DAB" xlink:to="loc_us-gaap_ReceivableTypeDomain_CAEFC554FD669DC9478BD99ED3341B86_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ReceivableTypeDomain" xlink:label="loc_us-gaap_ReceivableTypeDomain_CAEFC554FD669DC9478BD99ED3341B86" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_ABFE27E23330883965D2D99ED3319DAB" xlink:to="loc_us-gaap_ReceivableTypeDomain_CAEFC554FD669DC9478BD99ED3341B86" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_CardSettlementsDueFromMerchantsMember" xlink:label="loc_prth_CardSettlementsDueFromMerchantsMember_18D6F562CF6465C8A262D99ED3358D6B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReceivableTypeDomain_CAEFC554FD669DC9478BD99ED3341B86" xlink:to="loc_prth_CardSettlementsDueFromMerchantsMember_18D6F562CF6465C8A262D99ED3358D6B" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_CardSettlementsDueFromProcessorsMember" xlink:label="loc_prth_CardSettlementsDueFromProcessorsMember_80EE0E44F723B9061184D99ED34400AB" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReceivableTypeDomain_CAEFC554FD669DC9478BD99ED3341B86" xlink:to="loc_prth_CardSettlementsDueFromProcessorsMember_80EE0E44F723B9061184D99ED34400AB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueByLiabilityClassAxis" xlink:label="loc_us-gaap_FairValueByLiabilityClassAxis_2566AFDD3B7C9DD375D1D99ED347376C" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_CD8DE929CD3AB1E11A9DD99ED33064FB" xlink:to="loc_us-gaap_FairValueByLiabilityClassAxis_2566AFDD3B7C9DD375D1D99ED347376C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_824ED60A2024D5F9944BD99ED347DA69_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_2566AFDD3B7C9DD375D1D99ED347376C" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_824ED60A2024D5F9944BD99ED347DA69_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_824ED60A2024D5F9944BD99ED347DA69" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_2566AFDD3B7C9DD375D1D99ED347376C" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_824ED60A2024D5F9944BD99ED347DA69" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_CardSettlementsDueToMerchantsMember" xlink:label="loc_prth_CardSettlementsDueToMerchantsMember_FD30E7CD6D8DF3C2D85DD99ED348FD5D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_824ED60A2024D5F9944BD99ED347DA69" xlink:to="loc_prth_CardSettlementsDueToMerchantsMember_FD30E7CD6D8DF3C2D85DD99ED348FD5D" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_DueToACHPayeesMember" xlink:label="loc_prth_DueToACHPayeesMember_5EB464276B63B6E5EAABD99ED34D54EB" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_824ED60A2024D5F9944BD99ED347DA69" xlink:to="loc_prth_DueToACHPayeesMember_5EB464276B63B6E5EAABD99ED34D54EB" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_MerchantReservesHeldBySponsorBanks" xlink:label="loc_prth_MerchantReservesHeldBySponsorBanks_56E073C0BD9336C98218D99ED34E89A1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_3497D1DCD2F4A3FE7FEDD99ED34EF203" xlink:to="loc_prth_MerchantReservesHeldBySponsorBanks_56E073C0BD9336C98218D99ED34E89A1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SettlementAssetsCurrent" xlink:label="loc_us-gaap_SettlementAssetsCurrent_72AEA3559AFB0225DECED99ED34FF136" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_3497D1DCD2F4A3FE7FEDD99ED34EF203" xlink:to="loc_us-gaap_SettlementAssetsCurrent_72AEA3559AFB0225DECED99ED34FF136" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SettlementLiabilitiesCurrent" xlink:label="loc_us-gaap_SettlementLiabilitiesCurrent_6DB80E80EE89BC1C721DD99ED34F0246" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_3497D1DCD2F4A3FE7FEDD99ED34EF203" xlink:to="loc_us-gaap_SettlementLiabilitiesCurrent_6DB80E80EE89BC1C721DD99ED34F0246" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://miacquisitions.com/role/SettlementAssetsAndObligationsTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://miacquisitions.com/role/StockBasedCompensationPlans" xlink:type="extended" />
  <link:definitionLink xlink:role="http://miacquisitions.com/role/StockBasedCompensationPlansSummaryOfEquityBasedCompensationExpenseDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_96F8AE64E86B2A4A25ABDE6348806A0C" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_22E4800ECA98AD7735C6DE63487E20F6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_96F8AE64E86B2A4A25ABDE6348806A0C" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_22E4800ECA98AD7735C6DE63487E20F6" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PlanNameAxis" xlink:label="loc_us-gaap_PlanNameAxis_DFC51D853355EEEED86CDE63487FFBFA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_22E4800ECA98AD7735C6DE63487E20F6" xlink:to="loc_us-gaap_PlanNameAxis_DFC51D853355EEEED86CDE63487FFBFA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PlanNameDomain" xlink:label="loc_us-gaap_PlanNameDomain_053B4260F7C3F466B140DE63487F6C7A_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_DFC51D853355EEEED86CDE63487FFBFA" xlink:to="loc_us-gaap_PlanNameDomain_053B4260F7C3F466B140DE63487F6C7A_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PlanNameDomain" xlink:label="loc_us-gaap_PlanNameDomain_053B4260F7C3F466B140DE63487F6C7A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_DFC51D853355EEEED86CDE63487FFBFA" xlink:to="loc_us-gaap_PlanNameDomain_053B4260F7C3F466B140DE63487F6C7A" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_A2018EquityIncentivePlanMember" xlink:label="loc_prth_A2018EquityIncentivePlanMember_7C5A45C7B139C0B28574DE63488045BF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_053B4260F7C3F466B140DE63487F6C7A" xlink:to="loc_prth_A2018EquityIncentivePlanMember_7C5A45C7B139C0B28574DE63488045BF" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_A2014ManagementIncentivePlanMember" xlink:label="loc_prth_A2014ManagementIncentivePlanMember_EFF316046ABC96E4E49EDE6348802A8A" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_053B4260F7C3F466B140DE63487F6C7A" xlink:to="loc_prth_A2014ManagementIncentivePlanMember_EFF316046ABC96E4E49EDE6348802A8A" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_DeferredCompensationShareBasedArrangementsExpense" xlink:label="loc_prth_DeferredCompensationShareBasedArrangementsExpense_5B15755180CB71B6FA67DE76950D2292" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_96F8AE64E86B2A4A25ABDE6348806A0C" xlink:to="loc_prth_DeferredCompensationShareBasedArrangementsExpense_5B15755180CB71B6FA67DE76950D2292" xlink:type="arc" />
    <link:loc xlink:href="prth-20200630.xsd#prth_ShareBasedPaymentArrangementExpenseExcludingDeferredCompensationShareBasedArrangementsExpense" xlink:label="loc_prth_ShareBasedPaymentArrangementExpenseExcludingDeferredCompensationShareBasedArrangementsExpense_D83B5E0156BEE24B57B1DE6A63D1636D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_96F8AE64E86B2A4A25ABDE6348806A0C" xlink:to="loc_prth_ShareBasedPaymentArrangementExpenseExcludingDeferredCompensationShareBasedArrangementsExpense_D83B5E0156BEE24B57B1DE6A63D1636D" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://miacquisitions.com/role/StockBasedCompensationPlansTables" xlink:type="extended" />
</link:linkbase>
