What is a PK'er or PK switch?
What is a griefer?

Playerkiller, guy running around killing other players.....

FPS's are rumoured to be full of them.....

A griefer is somebody who PK's others for the sole purpose of ruining their game.

A PK (Player-killer) is somebody who kills others for the sake of killing. This is one type of griefer.

A PK switch is something used in other games (such as EQ and AC) to turn on and off a flag that makes you vulnerable to attacks by other people who have gone PK (PvP+). The PK switch does not exist in SWG, as you are vulnerable to attack at any time you're not in a truce zone.

A griefer is someone who's one goal in a game is to purposely make others unhappy. This happens a number of ways.. stealing, cheating, kill-stealing, quest-jumping, pking, etc.

CS is the king of grief gaming in my humble opinion....