1. to be disloyal to someone who trusts you
2. to reveal or expose something that should be kept secret
3. to show or indicate something unintentionally

Examples

• He felt betrayed when his best friend told everyone his secret.
• The spy betrayed his country by selling classified information.
• She promised not to betray his trust.
• His nervous laughter betrayed his anxiety about the test.
• The witness betrayed the criminal’s location to the police.
• Her trembling hands betrayed her fear.
• They betrayed the resistance fighters to the enemy.