<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019f38c2-9862-7153-8616-f6bff107174e,g:e2cbe454-7f03-4d49-aed1-4fd8eb3f37e5-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://xbrl.sec.gov/oef/role/SeriesOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#SeriesOnly"/>
  <link:definitionLink xlink:role="http://xbrl.sec.gov/oef/role/SeriesOnly" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001359057_S000055882Member_019f38c2-9862-71f7-8303-eac8697b2cda" xlink:href="ck0001359057-20260723.xsd#ck0001359057_S000055882Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain" xlink:to="loc_ck0001359057_S000055882Member_019f38c2-9862-71f7-8303-eac8697b2cda" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://xbrl.sec.gov/oef/role/ClassOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#ClassOnly"/>
  <link:definitionLink xlink:role="http://xbrl.sec.gov/oef/role/ClassOnly" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_oef_ShareClassDomain" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#oef_ShareClassDomain"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001359057_C000176027Member_019f38c2-9862-7a09-a89d-23c19b093928" xlink:href="ck0001359057-20260723.xsd#ck0001359057_C000176027Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_ShareClassDomain" xlink:to="loc_ck0001359057_C000176027Member_019f38c2-9862-7a09-a89d-23c19b093928" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://xbrl.sec.gov/rr/role/RiskOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#RiskOnly"/>
  <link:definitionLink xlink:role="http://xbrl.sec.gov/rr/role/RiskOnly" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_oef_AllRisksMember" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#oef_AllRisksMember"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001359057_GeneralMarketRiskRecentMarketEventsRiskMember_019f38c2-9862-7acb-bbe5-15a1d46bfe6a" xlink:href="ck0001359057-20260723.xsd#ck0001359057_GeneralMarketRiskRecentMarketEventsRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001359057_GeneralMarketRiskRecentMarketEventsRiskMember_019f38c2-9862-7acb-bbe5-15a1d46bfe6a" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001359057_ManagementRiskMember_019f38c2-9862-71f8-8f40-cc036d599677" xlink:href="ck0001359057-20260723.xsd#ck0001359057_ManagementRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001359057_ManagementRiskMember_019f38c2-9862-71f8-8f40-cc036d599677" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001359057_FixedIncomeSecuritiesRiskMember_019f38c2-9862-7efb-8ace-ecd40047fc7b" xlink:href="ck0001359057-20260723.xsd#ck0001359057_FixedIncomeSecuritiesRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001359057_FixedIncomeSecuritiesRiskMember_019f38c2-9862-7efb-8ace-ecd40047fc7b" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001359057_FixedIncomeSecuritiesRiskCreditRiskMember_019f38c2-9862-7260-9bdb-0859fd884c92" xlink:href="ck0001359057-20260723.xsd#ck0001359057_FixedIncomeSecuritiesRiskCreditRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001359057_FixedIncomeSecuritiesRiskCreditRiskMember_019f38c2-9862-7260-9bdb-0859fd884c92" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001359057_FixedIncomeSecuritiesRiskInterestRateRiskMember_019f38c2-9862-735f-9960-7f17693b742a" xlink:href="ck0001359057-20260723.xsd#ck0001359057_FixedIncomeSecuritiesRiskInterestRateRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001359057_FixedIncomeSecuritiesRiskInterestRateRiskMember_019f38c2-9862-735f-9960-7f17693b742a" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001359057_FixedIncomeSecuritiesRiskCallOrPrepaymentRiskMember_019f38c2-9862-7348-88fd-07436ca6b18e" xlink:href="ck0001359057-20260723.xsd#ck0001359057_FixedIncomeSecuritiesRiskCallOrPrepaymentRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001359057_FixedIncomeSecuritiesRiskCallOrPrepaymentRiskMember_019f38c2-9862-7348-88fd-07436ca6b18e" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001359057_FixedIncomeSecuritiesRiskExtensionRiskMember_019f38c2-9862-7806-89a4-b55b3c54892a" xlink:href="ck0001359057-20260723.xsd#ck0001359057_FixedIncomeSecuritiesRiskExtensionRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001359057_FixedIncomeSecuritiesRiskExtensionRiskMember_019f38c2-9862-7806-89a4-b55b3c54892a" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001359057_USGovernmentAndUSAgencyObligationsRiskMember_019f38c2-9862-76a6-a043-1607a4dd81a5" xlink:href="ck0001359057-20260723.xsd#ck0001359057_USGovernmentAndUSAgencyObligationsRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001359057_USGovernmentAndUSAgencyObligationsRiskMember_019f38c2-9862-76a6-a043-1607a4dd81a5" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001359057_OtherInvestmentCompaniesRiskMember_019f38c2-9862-7efb-8b49-8f8a9d34c494" xlink:href="ck0001359057-20260723.xsd#ck0001359057_OtherInvestmentCompaniesRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001359057_OtherInvestmentCompaniesRiskMember_019f38c2-9862-7efb-8b49-8f8a9d34c494" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001359057_MunicipalSecuritiesRiskMember_019f38c2-9862-7540-b398-80acdc44acb2" xlink:href="ck0001359057-20260723.xsd#ck0001359057_MunicipalSecuritiesRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001359057_MunicipalSecuritiesRiskMember_019f38c2-9862-7540-b398-80acdc44acb2" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001359057_InflationRiskMember_019f38c2-9862-79c7-9fb2-7c56b780bd3c" xlink:href="ck0001359057-20260723.xsd#ck0001359057_InflationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001359057_InflationRiskMember_019f38c2-9862-79c7-9fb2-7c56b780bd3c" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001359057_DeflationRiskMember_019f38c2-9862-7515-b7c3-50b44c14384d" xlink:href="ck0001359057-20260723.xsd#ck0001359057_DeflationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001359057_DeflationRiskMember_019f38c2-9862-7515-b7c3-50b44c14384d" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001359057_BankingIndustryConcentrationRiskMember_019f38c2-9862-7b69-9594-dcdc1b800a29" xlink:href="ck0001359057-20260723.xsd#ck0001359057_BankingIndustryConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001359057_BankingIndustryConcentrationRiskMember_019f38c2-9862-7b69-9594-dcdc1b800a29" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001359057_CybersecurityRiskMember_019f38c2-9862-7d26-b898-b9178cdc0783" xlink:href="ck0001359057-20260723.xsd#ck0001359057_CybersecurityRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001359057_CybersecurityRiskMember_019f38c2-9862-7d26-b898-b9178cdc0783" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001359057_OperationalRiskMember_019f38c2-9862-7b7c-84b8-cf6259e4af61" xlink:href="ck0001359057-20260723.xsd#ck0001359057_OperationalRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001359057_OperationalRiskMember_019f38c2-9862-7b7c-84b8-cf6259e4af61" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001359057_ArtificialIntelligenceRiskMember_019f8a65-95e6-7478-bfe7-5ba411de94df" xlink:href="ck0001359057-20260723.xsd#ck0001359057_ArtificialIntelligenceRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001359057_ArtificialIntelligenceRiskMember_019f8a65-95e6-7478-bfe7-5ba411de94df" xlink:type="arc" order="24"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://xbrl.sec.gov/rr/role/PerformanceMeasureOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#PerformanceMeasureOnly"/>
  <link:definitionLink xlink:role="http://xbrl.sec.gov/rr/role/PerformanceMeasureOnly" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_oef_PerformanceMeasureDomain" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#oef_PerformanceMeasureDomain"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001359057_BloombergU.S.AggregateBondIndexReflectsNoDeductionsForFeesExpensesOrTaxesIndexMember_019f38c2-9862-7fbf-b8b9-e6847268740f" xlink:href="ck0001359057-20260723.xsd#ck0001359057_BloombergU.S.AggregateBondIndexReflectsNoDeductionsForFeesExpensesOrTaxesIndexMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_PerformanceMeasureDomain" xlink:to="loc_ck0001359057_BloombergU.S.AggregateBondIndexReflectsNoDeductionsForFeesExpensesOrTaxesIndexMember_019f38c2-9862-7fbf-b8b9-e6847268740f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001359057_Bloomberg13YearUSGovernmentCreditIndexreflectsnodeductionforfeesexpensesortaxesIndexMember_019f38c2-9862-7726-ae0d-61964c985ab4" xlink:href="ck0001359057-20260723.xsd#ck0001359057_Bloomberg13YearUSGovernmentCreditIndexreflectsnodeductionforfeesexpensesortaxesIndexMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_PerformanceMeasureDomain" xlink:to="loc_ck0001359057_Bloomberg13YearUSGovernmentCreditIndexreflectsnodeductionforfeesexpensesortaxesIndexMember_019f38c2-9862-7726-ae0d-61964c985ab4" xlink:type="arc" order="4"/>
  </link:definitionLink>
</link:linkbase>
