A bandeau bikini is a bikini whose top is strapless. It may be fastened in the front or back or it may also be elastic enough not to require any fastener. Bandeau comes from the French word bande or strip. Its plural is bandeaux.
Bandeau Bikini: A popular swim wear
The bandeau bikini has two edges, although that is commonly made with a detachable halter strap which goes around the neck. A wide bandeau that goes around the midriff is also known as a "tube top."