Frag

The term frag originates from military slang, where it means to kill a soldier on your own side, especially a superior officer. In Doom and other FPS games, frag refers to the act of killing another player's character in the game. In cooperative mode, there is a frag count indicating how many times you killed your allies, accidentally or otherwise. When deathmatch mode was implemented, frags were used as a measure of score. Each kill of an opponent earns a frag, while suiciding subtracts one. At the end of the deathmatch, whoever has the most frags is the winner.

Frag is also occasionally extended to mean killing monsters as well.