betray |biˈtrā|
verb [ trans. ]
be disloyal to : his friends were shocked when he betrayed them.
• be disloyal to (one's country, organization, or ideology) by acting in the interests of an enemy : he could betray his country for the sake of communism.
• treacherously inform an enemy of the existence or location of (a person or organization) : this group was betrayed by an informer.
• treacherously reveal (secrets or information) : many of those employed by diplomats betrayed secrets and sold classified documents.
• figurative reveal the presence of; be evidence of : she drew a deep breath that betrayed her indignation.
DERIVATIVES
betrayal |-əl| noun
betrayer noun
ORIGIN Middle English : from be- [thoroughly] + obsolete tray [betray,] from Old French trair, based on Latin tradere ‘hand over.’ Compare with traitor .

Thesaurus
betrayal
noun
betrayal in the workplace | the CIA leak was a serious act of betrayal disloyalty, treachery, bad faith, faithlessness, falseness, duplicity, deception, double-dealing; breach of faith, breach of trust, stab in the back; double-cross, sellout; literary perfidy. antonym loyalty.