Answer: Nerfed
The advent of online multiplayer gaming introduced an element of game design that designers hadn’t previously had to wrangle with: balancing character abilities and in-game items so that game play was fair and didn’t encourage players to flock to a certain character class or only use a specific weapon or gear combination.
With nearly every multiplayer game, there are updates and revisions over time to rebalance and adjust areas that developers consider problematic such as weapon/armor combinations that stack to give unreasonably powerful bonuses, or character-class skills that prove to be too effective or the like.
When developers make adjustments to weapons, gear, or skills in such a fashion that it decreases the effectiveness of the aforementioned thing, players say that the thing has been “nerfed”. The term, which originated in the Ultima Online community, is a reference to Nerf toys (specifically to how a Nerf football or toy weapon is a softer, less dangerous version of the real thing).
Image courtesy of Nerf.