Definition of Nerf in US English:

Nerf

noun

trademark
  • A type of foam rubber used to make toys and sports equipment.

    ‘Would nothing be dangerous if everything was made out of Nerf?’
    as modifier ‘a Nerf football’

verb

[with object]US
informal
  • 1Cause to be weak or ineffective.

    ‘the constant zone running nerfed Michigan's pass rush’
    ‘the government is nerfing our upload speeds’
    1. 1.1 (of a video game developer) reduce the power of (a character, weapon, etc.) in a new installment or update of a video game.
      ‘ever since they nerfed the shield, the game just isn't as fun’
      ‘the most used rifle has been subjected to nerfing’

Origin

1970s: apparently an arbitrary formation.

Pronunciation

Nerf

/nərf//nərf/