Underwear that women reserve for when they are having their periods. These are often no longer a woman’s favorites, or they can be budget wear. Some women wear dark panties during their periods, so they don’t have to worry about stains. Not the same as Period Underwear, which are a recent invention meant to replace pads and tampons, and may have been manufactured with some funky (as in potentially harmful) ingredients called PFAS or short chain per-and polyfluoroalkyl substances.