ban·deau 
(băn-dō)
(băn-dō)n. pl. ban·deaux (-dōz) or ban·deaus
1. A narrow band for the hair.
2.
a. A garment consisting of a band of fabric that covers the bust, sometimes having removable straps.
b. A usually strapless brassiere.
adj.
Of, relating to, or being a garment having a band of fabric that covers the bust: a bandeau bikini.
[French, from Old French bandel, diminutive of bande, band, strip; see BAND1.]