The term is used by players of computer games (not just Guild Wars) to mean the reducing of certain content's effectiveness that the developers of the game have deemed unbalanced, over-used or an exploit (e.g. reducing the bonus of certain weapons, reducing the damage of certain spells, etc.).
The opposite of a nerf, i.e. making something stronger or more effective is usually called a "buff". However, the two terms often blend in with each other, if, for example, the monsters in a particular farming spot are "buffed", it can be said that the farming spot has been "nerfed". Similar comparisons can also be made in the PvP community.
Nerfing is usually done by releasing a game update. In Guild Wars, there is no way to avoid "nerfing" as updates are automatically downloaded.
Examples of nerfing done in Guild Wars:
- The spell Chain Lightning was made weaker in the summer of 2005 by reducing its damage and increasing its activation time. This made it less potent and easier to disrupt. This was in response to the domination of PvP teams that were composed of Air Magic spikers.
- The explorable areas Witman's Folly and the Underworld had new/modified monsters introduced to make them harder for players to farm "solo." The additions and modifications comprised of adding an enchantment removing creature because enchantments were the secret to being able to farm that area alone.
- Around the release of Factions, the number of minions was capped based on the player's rank in Death Magic. This was to place a cap on the effectiveness of minion masters.