Merriam-Webster Collegiate Dictionary - petticoat

 I. noun  Etymology: Middle English petycote short tunic, ~, from pety small + cote coat  Date: 15th century  1. a skirt worn by women, girls, or young children: as  a. an outer skirt formerly worn by women and small children  b. a fancy skirt made to show below a draped-up overskirt  c. an underskirt usually a little shorter than outer clothing and often made with a ruffled, pleated, or lace edge  d. archaic the skirt of a woman's riding habit  2.  a. a garment characteristic or typical of women  b. woman  3. something (as a valance) resembling a ~  • ~ed adjective  II. adjective  Date: 1660 of, relating to, or exercised by women ; female