betray
verb.
reveal unintentionally
Her smile betrayed her true feelings
Synonym: bewray
verb.
deliver to an enemy by treachery
Judas sold Jesus|The spy betrayed his country
Synonym: sell
verb.
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
Synonym: fail
verb.
be sexually unfaithful to one's partner in marriage
She cheats on her husband|Might her husband be wandering?
verb.
give away information about somebody
He told on his classmate who had cheated on the exam
verb.
cause someone to believe an untruth
The insurance company deceived me when they told me they were covering my house