A skirt stiffened with hoops WordNet 3.0 & Open English WordNet

A hoop skirt or hoopskirt is a women's undergarment worn in various periods to hold the skirt extended into a fashionable shape. Wikipedia

Shaped framework of reed, cane, or steel, used to support women's dresses in the fashionable silhouette of a particular period Wikidata

A skirt stiffened with hoops. Wiktionary

A women's undergarment worn in various historical periods to hold the skirt extended into a fashionable shape, typically consisting of a fabric petticoat with casings to hold a stiffening material, variously rope, osiers, whalebone, steel, or nylon. Wiktionary

Undergarment. Wiktionary (translation)