With respect to EverQuest, nerfing means for Verant to change some element of the game, such as whether or not a piece of loot drops or how monsters act in the game so as to make it harder for the player to enjoy and play the game. It is particularly considered a serious nerf if the change is to a part of the game that has been around for a long time (i.e. more than a few months). This is because by this time people feel that the element changed has been sufficiently tested by the community and it has become an integral part of the game. Note that a change is only considered nerfing if it makes the playing environment less friendly for the players.