Betray (verb)

1. To be unfaithful to (a person, cause, or organization), typically by aiding an enemy.
2. To reveal (something) unexpectedly and unintentionally.
3. To fail to support or defend (someone) when they need it.

Origin:

Middle english: from old french trair, from latin tradere "hand over, betray", from trans- "across" + dare "give".

Examples:

1. He was accused of betraying his country by passing secrets to the enemy.
2. She felt betrayed when her best friend kept the secret from her.
3. It was a betrayal of trust when he shared the confidential information with a competitor.
4. The company's decision to close the factory was a betrayal of its workers.
5. The government"s failure to act on the issue betrayed the public"s trust.