Whenever you do something like kill a random person for no reason whatsoever and then it comes back at you that is know as Game Karma.
it can mean for anything you do bad to someone in the game.
But Game Karma can be also good but that is if you do random acts of kindness in the game such as saving lives and giving donations.
Guy 1: Holy crap i just got killed for no reason.
Guy 2: Major Game Karma...
Guy 1: Shut up!