bathing costume vs garment

bathing costume and garment both are nouns.

Word	Noun	Adjective	Verb	Adverb
bathing costume	Yes	No	No	No
garment	Yes	No	Yes	No

As nouns, garment is a hypernym of bathing costume; that is, garment is a word with a broader meaning than bathing costume:

bathing costume (noun)	garment (noun)
tight fitting garment worn for swimming	an article of clothing

bathing costume (verb)	garment (verb)
	provide with clothes or put clothes on