<?xml version="1.0" encoding="US-ASCII" standalone="no"?>
    <!-- Field: Doc-Info; Name: Generator; Value: GoFiler Complete; Version: 6.5b -->
    <!-- Field: Doc-Info; Name: VendorURI; Value: https://www.novaworks.com -->
    <!-- Field: Doc-Info; Name: Status; Value: 0x00000000 -->
<link:linkbase xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xmlns:xbrli="http://www.xbrl.org/2003/instance" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#HoldingsByIndustrySector" roleURI="http://xbrl.sec.gov/oef/role/HoldingsByIndustrySector" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#HoldingsByGeographicRegion" roleURI="http://xbrl.sec.gov/oef/role/HoldingsByGeographicRegion" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#HoldingsByCreditQuality" roleURI="http://xbrl.sec.gov/oef/role/HoldingsByCreditQuality" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#HoldingsByMaturity" roleURI="http://xbrl.sec.gov/oef/role/HoldingsByMaturity" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#HoldingsByAssetCategory" roleURI="http://xbrl.sec.gov/oef/role/HoldingsByAssetCategory" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#HoldingsByOtherCategory" roleURI="http://xbrl.sec.gov/oef/role/HoldingsByOtherCategory" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#HoldingsByOtherCategory2" roleURI="http://xbrl.sec.gov/oef/role/HoldingsByOtherCategory2" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#LargestHoldings" roleURI="http://xbrl.sec.gov/oef/role/LargestHoldings" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#ProspectusOnly" roleURI="http://xbrl.sec.gov/rr/role/ProspectusOnly" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#RiskOnly" roleURI="http://xbrl.sec.gov/rr/role/RiskOnly" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#CoregistrantOnly" roleURI="http://xbrl.sec.gov/oef/role/CoregistrantOnly" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#SeriesOnly" roleURI="http://xbrl.sec.gov/oef/role/SeriesOnly" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#ClassOnly" roleURI="http://xbrl.sec.gov/oef/role/ClassOnly" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#PerformanceMeasureOnly" roleURI="http://xbrl.sec.gov/rr/role/PerformanceMeasureOnly" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#HoldingAssetCategoryOnly" roleURI="http://xbrl.sec.gov/oef/role/HoldingAssetCategoryOnly" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#BroadBasedIndexOnly" roleURI="http://xbrl.sec.gov/oef/role/BroadBasedIndexOnly" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#AdditionalIndexOnly" roleURI="http://xbrl.sec.gov/oef/role/AdditionalIndexOnly" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#IndustrySectorOnly" roleURI="http://xbrl.sec.gov/oef/role/IndustrySectorOnly" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#GeographicRegionOnly" roleURI="http://xbrl.sec.gov/oef/role/GeographicRegionOnly" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#CreditQualityOnly" roleURI="http://xbrl.sec.gov/oef/role/CreditQualityOnly" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#MaturityOnly" roleURI="http://xbrl.sec.gov/oef/role/MaturityOnly" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#Other1CategoryOnly" roleURI="http://xbrl.sec.gov/oef/role/Other1CategoryOnly" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#Other2CategoryOnly" roleURI="http://xbrl.sec.gov/oef/role/Other2CategoryOnly" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#LargestHoldingOnly" roleURI="http://xbrl.sec.gov/oef/role/LargestHoldingOnly" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#SalesLoadOnly" roleURI="http://xbrl.sec.gov/oef/role/SalesLoadOnly" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#HoldingMeasureOnly" roleURI="http://xbrl.sec.gov/oef/role/HoldingMeasureOnly" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#ValueMeasureOnly" roleURI="http://xbrl.sec.gov/oef/role/ValueMeasureOnly" />
    <link:arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension" arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" />
    <link:arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain" arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" />
    <link:arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member" arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" />
    <link:arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all" arcroleURI="http://xbrl.org/int/dim/arcrole/all" />
    <link:arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#notAll" arcroleURI="http://xbrl.org/int/dim/arcrole/notAll" />
    <link:arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default" arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" />
    <link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/rr/role/ProspectusOnly" />
    <link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/rr/role/RiskOnly">
      <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#oef_AllRisksMember" xlink:label="loc_oefAllRisksMember" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_ActiveManagementRiskMember" xlink:label="loc_rbbActiveManagementRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_rbbActiveManagementRiskMember" xlink:type="arc" order="0" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_AffiliatedFundRiskMember" xlink:label="loc_rbbAffiliatedFundRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_rbbAffiliatedFundRiskMember" xlink:type="arc" order="10" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_AssetClassRiskMember" xlink:label="loc_rbbAssetClassRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_rbbAssetClassRiskMember" xlink:type="arc" order="20" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_CallRiskMember" xlink:label="loc_rbbCallRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_rbbCallRiskMember" xlink:type="arc" order="30" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_CashOrCashEquivalentsRiskMember" xlink:label="loc_rbbCashOrCashEquivalentsRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_rbbCashOrCashEquivalentsRiskMember" xlink:type="arc" order="40" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_ConcentrationRiskMember" xlink:label="loc_rbbConcentrationRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_rbbConcentrationRiskMember" xlink:type="arc" order="50" />
      <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditRiskMember" xlink:label="loc_us-gaapCreditRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_us-gaapCreditRiskMember" xlink:type="arc" order="60" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_CyberSecurityRiskMember" xlink:label="loc_rbbCyberSecurityRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_rbbCyberSecurityRiskMember" xlink:type="arc" order="70" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_DerivativesRiskMember" xlink:label="loc_rbbDerivativesRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_rbbDerivativesRiskMember" xlink:type="arc" order="80" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_DurationRiskMember" xlink:label="loc_rbbDurationRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_rbbDurationRiskMember" xlink:type="arc" order="90" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_EtfRiskMember" xlink:label="loc_rbbEtfRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_rbbEtfRiskMember" xlink:type="arc" order="100" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_FixedIncomeMarketRiskMember" xlink:label="loc_rbbFixedIncomeMarketRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_rbbFixedIncomeMarketRiskMember" xlink:type="arc" order="110" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_FixedIncomeSecuritiesRiskMember" xlink:label="loc_rbbFixedIncomeSecuritiesRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_rbbFixedIncomeSecuritiesRiskMember" xlink:type="arc" order="120" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_FundOfFundsRiskMember" xlink:label="loc_rbbFundOfFundsRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_rbbFundOfFundsRiskMember" xlink:type="arc" order="130" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_FuturesRiskMember" xlink:label="loc_rbbFuturesRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_rbbFuturesRiskMember" xlink:type="arc" order="140" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_HighPortfolioTurnoverRiskMember" xlink:label="loc_rbbHighPortfolioTurnoverRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_rbbHighPortfolioTurnoverRiskMember" xlink:type="arc" order="150" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_IncomeRiskMember" xlink:label="loc_rbbIncomeRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_rbbIncomeRiskMember" xlink:type="arc" order="160" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_InflationRiskMember" xlink:label="loc_rbbInflationRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_rbbInflationRiskMember" xlink:type="arc" order="170" />
      <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestRateRiskMember" xlink:label="loc_us-gaapInterestRateRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_us-gaapInterestRateRiskMember" xlink:type="arc" order="180" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_IssuerRiskMember" xlink:label="loc_rbbIssuerRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_rbbIssuerRiskMember" xlink:type="arc" order="190" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_LiquidityRiskMember" xlink:label="loc_rbbLiquidityRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_rbbLiquidityRiskMember" xlink:type="arc" order="200" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_ManagementRiskMember" xlink:label="loc_rbbManagementRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_rbbManagementRiskMember" xlink:type="arc" order="210" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_MarketRiskMember" xlink:label="loc_rbbMarketRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_rbbMarketRiskMember" xlink:type="arc" order="220" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_MarketPriceRiskMember" xlink:label="loc_rbbMarketPriceRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_rbbMarketPriceRiskMember" xlink:type="arc" order="230" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_MarketTradingRiskMember" xlink:label="loc_rbbMarketTradingRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_rbbMarketTradingRiskMember" xlink:type="arc" order="240" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_NewFundRiskMember" xlink:label="loc_rbbNewFundRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_rbbNewFundRiskMember" xlink:type="arc" order="250" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_OperationalRiskMember" xlink:label="loc_rbbOperationalRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_rbbOperationalRiskMember" xlink:type="arc" order="260" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_OptionsRiskMember" xlink:label="loc_rbbOptionsRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_rbbOptionsRiskMember" xlink:type="arc" order="270" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_PremiumDiscountRiskMember" xlink:label="loc_rbbPremiumDiscountRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_rbbPremiumDiscountRiskMember" xlink:type="arc" order="280" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_PrepaymentAndExtensionRiskMember" xlink:label="loc_rbbPrepaymentAndExtensionRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_rbbPrepaymentAndExtensionRiskMember" xlink:type="arc" order="290" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_PricingRiskMember" xlink:label="loc_rbbPricingRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_rbbPricingRiskMember" xlink:type="arc" order="300" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_RatingAgenciesRiskMember" xlink:label="loc_rbbRatingAgenciesRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_rbbRatingAgenciesRiskMember" xlink:type="arc" order="310" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_ReinvestmentRiskMember" xlink:label="loc_rbbReinvestmentRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_rbbReinvestmentRiskMember" xlink:type="arc" order="320" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_ReverseRepurchaseAgreementsRiskMember" xlink:label="loc_rbbReverseRepurchaseAgreementsRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_rbbReverseRepurchaseAgreementsRiskMember" xlink:type="arc" order="330" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_RiskOfInvestingInTheUSMember" xlink:label="loc_rbbRiskOfInvestingInTheUSMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_rbbRiskOfInvestingInTheUSMember" xlink:type="arc" order="340" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_SectorRiskMember" xlink:label="loc_rbbSectorRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_rbbSectorRiskMember" xlink:type="arc" order="350" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_SecuritiesLendingRiskMember" xlink:label="loc_rbbSecuritiesLendingRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_rbbSecuritiesLendingRiskMember" xlink:type="arc" order="360" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_TaxRiskMember" xlink:label="loc_rbbTaxRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_rbbTaxRiskMember" xlink:type="arc" order="370" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_UnderlyingFundsRiskMember" xlink:label="loc_rbbUnderlyingFundsRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_rbbUnderlyingFundsRiskMember" xlink:type="arc" order="380" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_USGovernmentObligationsRiskMember" xlink:label="loc_rbbUSGovernmentObligationsRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_rbbUSGovernmentObligationsRiskMember" xlink:type="arc" order="390" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_USTreasuryAndAgencyMarketRiskMember" xlink:label="loc_rbbUSTreasuryAndAgencyMarketRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_rbbUSTreasuryAndAgencyMarketRiskMember" xlink:type="arc" order="400" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_ValuationRiskMember" xlink:label="loc_rbbValuationRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_rbbValuationRiskMember" xlink:type="arc" order="410" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_InflationIndexedBondsRiskMember" xlink:label="loc_rbbInflationIndexedBondsRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_rbbInflationIndexedBondsRiskMember" xlink:type="arc" order="420" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_InflationLinkedSecuritiesRiskMember" xlink:label="loc_rbbInflationLinkedSecuritiesRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_rbbInflationLinkedSecuritiesRiskMember" xlink:type="arc" order="430" />
    </link:definitionLink>
    <link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/oef/role/CoregistrantOnly" />
    <link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/oef/role/SeriesOnly">
      <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain" xlink:label="loc_deiEntityDomain" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_S000105628Member" xlink:label="loc_rbbS000105628Member" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_deiEntityDomain" xlink:to="loc_rbbS000105628Member" xlink:type="arc" order="0" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_S000105625Member" xlink:label="loc_rbbS000105625Member" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_deiEntityDomain" xlink:to="loc_rbbS000105625Member" xlink:type="arc" order="10" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_S000105626Member" xlink:label="loc_rbbS000105626Member" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_deiEntityDomain" xlink:to="loc_rbbS000105626Member" xlink:type="arc" order="20" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_S000105627Member" xlink:label="loc_rbbS000105627Member" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_deiEntityDomain" xlink:to="loc_rbbS000105627Member" xlink:type="arc" order="30" />
    </link:definitionLink>
    <link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/oef/role/ClassOnly">
      <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#oef_ShareClassDomain" xlink:label="loc_oefShareClassDomain" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_C000276406Member" xlink:label="loc_rbbC000276406Member" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefShareClassDomain" xlink:to="loc_rbbC000276406Member" xlink:type="arc" order="0" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_C000276403Member" xlink:label="loc_rbbC000276403Member" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefShareClassDomain" xlink:to="loc_rbbC000276403Member" xlink:type="arc" order="10" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_C000276404Member" xlink:label="loc_rbbC000276404Member" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefShareClassDomain" xlink:to="loc_rbbC000276404Member" xlink:type="arc" order="20" />
      <link:loc xlink:type="locator" xlink:href="rbb-20260610.xsd#rbb_C000276405Member" xlink:label="loc_rbbC000276405Member" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefShareClassDomain" xlink:to="loc_rbbC000276405Member" xlink:type="arc" order="30" />
    </link:definitionLink>
    <link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/rr/role/PerformanceMeasureOnly" />
    <link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/oef/role/HoldingAssetCategoryOnly" />
    <link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/oef/role/BroadBasedIndexOnly" />
    <link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/oef/role/AdditionalIndexOnly" />
    <link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/oef/role/IndustrySectorOnly" />
    <link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/oef/role/GeographicRegionOnly" />
    <link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/oef/role/CreditQualityOnly" />
    <link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/oef/role/MaturityOnly" />
    <link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/oef/role/Other1CategoryOnly" />
    <link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/oef/role/Other2CategoryOnly" />
    <link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/oef/role/LargestHoldingOnly" />
    <link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/oef/role/SalesLoadOnly" />
    <link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/oef/role/HoldingMeasureOnly" />
    <link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/oef/role/ValueMeasureOnly" />
</link:linkbase>
