WordWeb Online

1. Reveal unintentionally
   "Her smile betrayed her true feelings"
   - bewray [archaic]
    
2. Deliver to an enemy by treachery
   "The spy betrayed his country"
   - sell
    
3. Disappoint, prove undependable to; abandon, forsake
   - fail
    
4. Be sexually unfaithful to one's partner in marriage
   - cheat on, cheat, cuckold, wander
    
5. Give away information about somebody
   - denounce, tell on, give away, rat, grass, shop, snitch, stag
    
6. Cause someone to believe an untruth
   - deceive, lead astray

Derived forms: betraying, betrays, betrayed

See also: betrayal, betrayer

Type of: break, bring out, cozen, deceive, delude, disappoint, disclose, discover, disinform, divulge, expose, give away, inform, lead on, let down, let on, let out, misinform, mislead, reveal, unwrap