means A stretchy synthetic fibre (a brand name for spandex/elastane) woven into clothing to make it cling, flex, and bounce back to shape.

from "Lycra" is a trademark coined by the chemical company DuPont, who introduced the elastic fibre in the mid-20th century. The fibre's generic name, spandex, is itself an anagram of "expands" — a rare case of chemists having a little fun with their letters. The underlying material is a polyurethane elastomer; "elastane," the name used in much of Europe, simply nods to its defining trick of elasticity. So Lycra is to spandex what Kleenex is to tissue: one company's name that stretched to cover the whole category.