Bandeau n. : A narrow band or fillet; a part of a head-dress.

Example:
Has anyone bought a Bandeau bathing suit from Victoria Secret that ties?

Taxonomy
bandeau, free encyclopedia, neck, band, silhouette, Bikini, brassiere, body, sports wear, halter, midriff, elastic material, foundation garments, search, diminutive, bind, centrally, garment.

Defination from the web:
bandeau has but two edges, although it is sometimes manufactured with a halter strap that goes around the neck. A wide bandeau that covers much of the midriff is sometimes called a tube top. ... The bandeau emerges as the top part of a deux-pièces swimsuit during the 1940s. ...