verb (v)

• reveal unintentionally(verb.communication)

  Example:
  Her smile betrayed her true feelings.
  

  Synonym:
  bewray
  

  source: wordnet30
• deliver to an enemy by treachery(verb.social)

  Example:
  The spy betrayed his country.
  

  Synonym:
  sell
  

  source: wordnet30
• disappoint, prove undependable to; abandon, forsake(verb.emotion)

  Synonym:
  fail
  

  source: wordnet30
• be sexually unfaithful to one's partner in marriage(verb.social)

  Synonym:
  cheat, cheat on, cuckold, wander
  

  source: wordnet30
• give away information about somebody(verb.communication)

  Synonym:
  denounce, give away, grass, rat, shit, shop, snitch, stag, tell on
  

  source: wordnet30
• cause someone to believe an untruth(verb.communication)

  Synonym:
  deceive, lead astray
  Antonym:
  undeceive
  

  source: wordnet30
• To deliver into the hands of an enemy by treachery or fraud, in violation of trust; to give up treacherously or faithlessly; as, an officer betrayed the city.(verb)

  source: webster1913