underwire

[ uhn-der-wahyuh r ]
/ ˈʌn dərˌwaɪər /

noun

a wire sewn into the underside of each cup of a brassiere, used for support and shape.
a brassiere with such wires.

Origin of underwire

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019