swimming costume

bathing costume

noun

mainly British any apparel worn for swimming or sunbathing, such as a woman's one-piece garment covering most of the torso but not the limbs

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012