ban·deau (b?n-d??)n. pl. ban·deaux (-d?z?) 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.]American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.bandeau (?bænd??) n, pl -deaux (-d??z) 1. (Clothing & Fashion) a narrow band of ribbon, velvet, etc, worn round the head2. (Clothing & Fashion) a bikini top in the form of narrow band of material[C18: from French, from Old French bandel a little band2]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014ban?deau (bæn?do?, ?bæn do?) n., pl. -deaux (-?do?z, -do?z) 1. a headband. 2. a narrow brassiere. [1700?10;