beater vs rug beater

beater and rug beater both are nouns.

Word	Noun	Adjective	Verb	Adverb
beater	Yes	No	No	No
rug beater	Yes	No	No	No

As nouns, rug beater is a hyponym of beater; that is, rug beater is a word with a more specific, narrower meaning than beater:

Other hyponyms of beater include carpet beater, eggbeater, eggwhisk.

beater (noun)	rug beater (noun)
an implement for beating	implement for beating dust out of carpets
a worker who rouses wild game from under cover for a hunter