strapless
n.n. a piece of clothing, like a dress or a bra, that does not have any straps to hold it up. It stays in place by the weight of the fabric or by a band around the body.
n. a garment or undergarment lacking shoulder straps for support. Often used to describe styles that rely on a wide band or the weight of the fabric to remain in place.
She wore a beautiful strapless dress to the wedding.
The designer created a collection of strapless evening gowns that relied on intricate beading to keep the fabric secure.
While strapless styles were once considered too revealing for formal occasions, they have since become a staple of modern evening wear, often paired with a matching bra for added support.
From strap + -less. The noun sense is by analogy of strap-on.