Typically applied to online regularly-changed/updated video games.
To "nerf" something means to reduce its 'power' or effectiveness within the
game. Often times this is to solve some problem in the
game (such as an 'overpowered' weapon/ability or super effective strategy), or to push the players in one direction or another (such as a new cosmetic/item/character).
Nerfs affect the 'meta' or prevailing strategy/characters/items used to win the
game. In this way nerfs also give control to the developer of how the players play the
game. i.e. nerfing a commonly used item to discourage the community from playing with it.
Some nerfs can be so drastic they change the very fundamentals of the
game, and are often a contributing factor to the size of the playerbase, for
good or bad.
Outside of games, this would again mean to reduce the things 'power' or 'effectiveness'. The exact analogy that gave birth to this term, is that of a Nerf
Gun, compared to a real
gun.
Oh man, they totally nerfed 'Titans Armor'! Guess I'll stop playing Golem now :/
They nerfed Irelia again?? Oh wait, its actually a buff. <-- (opposite of
nerf)
Great, so now all the
free-2-play guns are nerfed, guess I have to buy some to keep competitive. :(
