stab (someone) in the back
idiomPart ofstab
stab (someone) in the back — idiom
1. to harm someone who trusted you by being disloyal or betraying them, especially
1.idiom
Definition
to harm someone who trusted you by being disloyal or betraying them, especially when they are not expecting it
Example
Mathieu felt that his business partner had stabbed him in the back by sharing company secrets.
After years of friendship, Indra could not believe that her closest colleague would stab her in the back during the promotion process.