knuckles vs knuckle duster

knuckles and knuckle duster both are nouns.

Word	Noun	Adjective	Verb	Adverb
knuckles	Yes	No	No	No
knuckle duster	Yes	No	No	No

As nouns, knuckles and knuckle duster are synonyms defined as:

knuckles and knuckle duster: (used in the plural) a small metal weapon; worn over the knuckles on the back of the hand

Other synonyms of knuckles include brass knuckles, brass knucks, knucks.

knuckles (noun)	knuckle duster (noun)
(used in the plural) a small metal weapon; worn over the knuckles on the back of the hand	(used in the plural) a small metal weapon; worn over the knuckles on the back of the hand