From Longman Dictionary of Contemporary Englishbikinibi‧ki‧ni /bəˈkiːni/ ●●○ noun [countable] 
DCCDSSa set of clothes worn by women for swimming, which consists of a top part covering the breasts, and a bottom part
DCCDSSa set of clothes worn by women for swimming, which consists of a top part covering the breasts, and a bottom partExamples from the Corpus
bikini• But he was wearing a bikini, a pink bikini with big black spots all over it.• Not once, even in the most remote spots and island hideaways, has Diana forgotten to put on her bikini top.• A skinny blond in a blue-and-white-striped bikini sprayed himself with water from a plastic plant-mister.• Paul just knows it ... Claire tries on the bikini instead.• It is her first one not published in January, and the first to deal specifically with the bikini in mind.• Busty women in tiny bikinis passed out fliers for this show or that one.Origin bikini (1900-2000) French Bikini Atoll, after a nuclear bomb test was held there in 1946 