noun a thong or string bikini with only a slender piece of fabric passing between the cheeks of the buttocks US, 1991
butt floss
slang A thong, a type of underwear or bikini bottom with a strip of fabric that goes between the buttocks (likened to dental floss between two teeth). How do people wear butt floss like that at the beach? It's so embarrassing!I could never wear butt floss—it's too uncomfortable.