Dictionary

To bump lightly, whether accidentally or purposefully.

Example: A racer will often nerf another as a psychological tactic.

The deterioration, weakening or worsening of a character, a weapon, a spell, etc.

To cripple or weaken an element of a video game during its development (such as a character, a weapon, a spell, etc.).

Example: The lightning spell was originally pretty powerful, but in the sequel they nerfed it so it became completely useless.

To arbitrarily limit or reduce the capability of.