an atoll in the Marshall Islands; formerly used by the United States as a site for testing nuclear weapons
"The documentary traced the history of Bikini, revealing how it was once an idyllic island before becoming a test site for American nuclear weapons."
A brief two-piece bathing suit worn by women, especially one that exposes the midriff and navel.
"She hesitated before stepping out of the locker room in her new bikini, worried it might be too revealing for the beach party."
In plain English: A bikini is a two-piece swimsuit that covers only the breasts and the lower body.
"She wore a bright red bikini to the beach."
Usage: Use the word bikini to refer specifically to a woman's two-piece swimsuit that leaves the midriff exposed, rather than using it as a general term for any bathing suit. It is often paired with "bottoms" or described by style when discussing swimwear options.
Bikini atoll.
"The nuclear test conducted at Bikini Atoll left a lasting impact on the local islanders and their environment."
The word bikini comes from the name of an island in the Marshall Islands where the United States tested nuclear weapons in 1946. The term was chosen because designers hoped the new bathing suit would create as much excitement as those atomic blasts.