betray

reveal unintentionally; "Her smile betrayed her true feelings"

deliver to an enemy by treachery; "Judas sold Jesus"; "The spy betrayed his country"

disappoint, prove undependable to; abandon, forsake; "His sense of smell failed him this time"; "His strength finally failed him"; "His children failed him in the crisis"

be sexually unfaithful to one's partner in marriage; "She cheats on her husband"; "Might her husband be wandering?"

give away information about somebody; "He told on his classmate who had cheated on the exam"

cause someone to believe an untruth; "The insurance company deceived me when they told me they were covering my house"