bathing suit vs swimsuit

bathing suit and swimsuit both are nouns.

Word	Noun	Adjective	Verb	Adverb
bathing suit	Yes	No	No	No
swimsuit	Yes	No	No	No

As nouns, bathing suit and swimsuit are synonyms defined as:

Other synonyms of bathing suit include bathing costume, swimming costume, swimwear.

bathing suit (noun)	swimsuit (noun)
tight fitting garment worn for swimming	tight fitting garment worn for swimming