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!"