In addition to "Away From Keyboard", it's taken on the somewhat wiseass meaning of "A Free Kill" (mostly in FPS games) as you're not there to fight back. Can be annoying when a player is afk, especially in games such as Counter-Strike where one character is picked to carry the bomb. If they're not there, the team cannot win except by attrition (i.e. killing all of the other team instead of blowing up the target site.) because they can neither drop the bomb for another player, nor can they set it.