An "underwire" refers to a thin, flexible, and often curved metal or plastic piece that is sewn into the lower part of a bra cup. It provides support and shape to the breasts by fitting snugly beneath them. Full definition
The Anita Non-Padded Seamless Nursing Underwire Bra # 5068 is made of soft, breathable microfiber. (breakoutbras.com)
Classic bikini set with a high waisted shape, featuring a ruffle bra with underwire offering tons of support, adjustable and detachable shoulder straps for an easy fit, as well as matching tropical printed swim bottoms with ruched details. (zaful.com)
Antiperspirants are a primary source of aluminum, and they prevent us from sweating the carcinogenic metal toxins out through the skin, a situation that amplifies the risk for women who are also getting exposed to nickel from sweating while wearing underwire bras. (westonaprice.org)