bathing suit 
(British also bathing costume)
noun chiefly North American
A swimming costume.But as important as a sound back may be to us, summer is coming and we also want to look good in tank tops, bathing suits and strapless dresses....
- Not long ago, we were shopping for bathing suits and tank tops for those beautiful, hot summer days.
- They are basically extensions of Speedo bathing suits with just a little more spandex.
Synonyms
swimsuit, bathing suit, bathing dress, swimming trunks, trunks, swimwear, bikini;
British swimming costume
informal swimming togs, cossie
Australian informal bathers, swimmers