To weaken or make less dangerous. Taken from the "Nerf" brand name, which makes sports equipment toys out of a soft foam (e.g., the Nerf football is soft foam rather than the hard leather of a real football). Used frequently in the context of computer game balance changes.

A person with an outwardly dominant, masculine, or aggressive personality, but who also enthusiastically takes on the submissive or "bottom" role in the bedroom.

To make worse or weaken, usually in the context of weakening something in order to balance out a game.

To diminish the power or effectiveness of...
To make less potent.

Originally, this was a product line of foam based toys for children. It was adopted by the online gaming community to refer to the reduction in power of a game feature for the sake of balance.

This term is now seeing more widespread generic usage, usually in reference to mechanical devices, or personal powers within a business framework.

antonyms: Buff(v), Spike(v)

Usually in first person shooters and RPGs, when game developers think a weapon is far too powerful, and threatens the stability of the game, and weakens the aspects of that power drmatically to rebalance it.

Nerfs are grumpy, antlered herbivores, resembling yaks, raised on many planets, including Alderaan, Gestron and Corellia, for their milk and meat. Herders of the beasts are well known for being as scruffy looking and surly as their livestock, and to be called a "nerf herder" (as Han Solo is by Princess Leia) is considered a strong insult.

Never
Effective

Ratchet

Fix

Most of the time these things don't fix anything