transitive verb

1. 1. to help the enemy of (one's country, cause, etc.); be a traitor to
   2. to deliver or expose to an enemy traitorously
2. to break faith with; fail to meet the hopes of he betrayed my trust in him
3. to lead astray; deceive; specif., to seduce and then desert
4. to reveal unknowingly or against one's wishes his face betrays his fear
5. to reveal or show signs of; indicate the house betrays its age
6. to disclose (secret information, confidential plans, etc.)

Etymology: ME bitraien < be-, intens. + traien, betray < OFr trair < L tradere, to hand over: see treason