brass knuckles

American  

noun

1. a band of metal with four holes that fits over the upper fingers and that is gripped when a fist is made, used for increasing the effect of a blow with the fist.

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Usage

What else does brass knuckles mean? Brass knuckles are a piece of metal designed to fit around the fingers by the lower knuckles and gripped by the hand. They can pack a powerful, potentially lethal punch.How do you pronounce brass knuckles?[ bras nuhk-uhls ]

Etymology

Origin of brass knuckles

An Americanism dating back to 1850–55