COMMON If someone that you trust stabs you in the back, they secretly do something which hurts and betrays you. She was incredibly disloyal. She would be your friend to your face, and then stab you in the back. She felt betrayed, as though her daughter had stabbed her in the back. Note: You can also talk about a stab in the back, meaning an action or remark which hurts and betrays someone. It's a stab in the back for all Manchester United fans. Note: You can also talk about back-stabbing, meaning talk or gossip which is intended to harm someone. People begin to avoid one another, take sides, be drawn into gossip and back-stabbing.