betrayal
n. C / Un. an act of hurting someone who trusts you, such as a friend or partner. It happens when you break a promise or help an enemy.
n. the act of violating trust, confidence, or an inherited bond of loyalty. Often involves aiding an adversary or failing to uphold a moral or personal commitment.
Sharing her secret with the whole school was a huge betrayal.
He felt a deep sense of betrayal when he discovered his business partner had been stealing from the company.
The novel explores the psychological impact of political betrayal, focusing on how a single informant's actions destroyed an entire underground resistance movement.
From betray + -al.
Uncountable when referring to the abstract concept of disloyalty; countable when referring to specific instances or acts.