2. team-killing, i.e. in a FPS. More specifically, this is the term used when one team-kills in Halo/Halo 2.
2. Halo announcer: "Lost the lead! BETRAYAL!"
2. friends stabbing you in the back.
3. the most hurtful thing anyone can do.
person 2: like you too.
person 1: see you later
person 3: who was that
person 2: some psycho weirdo
person1: now i feel betrayal