1. to turn on someone you trust, or to have someone do the same to you.
2. team-killing, i.e. in a FPS. More specifically, this is the term used when one team-
kills in Halo/
Halo 2.
1. i had the worst betrayal the other day, when my best
friend whom i thought i trusted stole my
girlfriend.
2. Halo announcer: "Lost the lead! BETRAYAL!"