to deliver or expose to an enemy by treachery or disloyalty

Benedict Arnold betrayed his country.

to be unfaithful in guarding, maintaining, or fulfilling

to betray a trust.

to disappoint the hopes or expectations of; be disloyal to

to betray one's friends.

to reveal or disclose in violation of confidence

to betray a secret.

to reveal unconsciously (something one would preferably conceal)

Her nervousness betrays her insecurity.

to show or exhibit; reveal; disclose

an unfeeling remark that betrays his lack of concern.

to deceive, misguide, or corrupt

a young lawyer betrayed by political ambitions into irreparable folly.

to seduce and desert.

verb

be faithful , be loyal , defend , protect , support , be quiet , hide , keep secret

verb

abandon , be unfaithful , bite the hand that feeds you , blow the whistle * , bluff , break faith , break promise , break trust , break with , commit treason , cross , deceive , deliver up , delude , desert , double-cross , finger * , forsake , go back on , inform against , inform on , jilt , knife * , let down , mislead , play false , play judas , seduce , sell down the river , sell out , stab in the back * , take in * , trick , turn in , turn informer , turn state’s evidence , walk out on , blurt out , dime , disclose , evince , fink on , give away , inform , lay bare , let slip , make known , manifest , rat on , reveal , show , sing * , snitch * , spill , squeal * , stool , tattle , tell , tell on , uncover , unmask , blab , divulge , expose , let out , unveil , beguile , cozen , dupe , fool , hoodwink , humbug , take in , accuse , act the traitor , be false to , blow , discover , entrap , falsify , finger , give over to the enemy , give up treacherously , hoax , inveigle , peach , rat , sell , sing , slander , snare , snitch , squeal , traduce , undo