A girdle is a tight-fitting undergarment that supports the lower body. The purpose of a girdle is to make a person's waist and stomach look smaller and firmer.
Girdles are thought of as old-fashioned ladies' underwear these days, though they are still worn by some — and many others wear "foundation garments" that are essentially modern girdles. Before the late 1960s, many women wore girdles, until the availability around that time of control-top pantyhose. Another kind of girdle is simply a ring that encircles something — a belt, a band of bark around a tree, or the Earth's equator.