backstabbing
nounUK /ˈbækˌstæbɪŋ/
US /ˈbækˌstæbɪŋ/
Being mean to someone who trusts you, usually behind their back.
Telling her secret to everyone was a cruel act of backstabbing.
OTHER MEANINGS
2. The act of attacking someone unfairly when they are not expecting it.
The team felt his sudden criticism was pure backstabbing.
3. Harming a friend or ally secretly to gain an advantage.
She was hurt by the backstabbing among her closest friends.
4. A pattern of disloyal behavior toward people who rely on you.
The office was full of gossip and backstabbing.