maillot vs bathing costume

maillot and bathing costume both are nouns.

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

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

Other hypernyms of maillot include bathing suit, swimming costume, swimsuit, swimwear.

maillot (noun)	bathing costume (noun)
tights for dancers or gymnasts	tight fitting garment worn for swimming
a woman's one-piece bathing suit