Verb
1. reveal unintentionally;
"Her smile betrayed her true feelings"2. deliver to an enemy by treachery;
"Judas sold Jesus""The spy betrayed his country"3. 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"4. be sexually unfaithful to one's partner in marriage;
"She cheats on her husband""Might her husband be wandering?"5. give away information about somebody;
"He told on his classmate who had cheated on the exam"6. cause someone to believe an untruth;
"The insurance company deceived me when they told me they were covering my house"