to give up or reveal (somebody or something) to an enemy by treachery
to be a traitor to (somebody or something)
He betrayed his people
to deliver (somebody or something) to an enemy by treachery
to deceive (somebody) or be disloyal to them
to fail or desert (somebody), esp in time of need
to show (one's feelings, etc) inadvertently
She behaved very well and betrayed no emotion — Jane Austen
to be an outward sign of (an inner feeling)
His clenched hands betrayed his acute annoyance — Conan Doyle
to disclose (a secret), deliberately or unintentionally, in violation of confidence
betrayal noun
betrayer noun
[Middle English betrayen, from be- + trayen to betray, from Old French traïr from Latin tradere: see traitor]