A petticoat is a women's undergarment, generally designed to be slightly stiff, so that it will inflate skirts or dresses worn over it. A woman wearing a petticoat has full, flounced skirts, along with the illusion of a slim waistline. Petticoats have been included in women's undergarments for centuries, waxing and waning in popularity. They are unlikely to disappear entirely, as full skirts and petticoats keep returning in the fashion cycle. Most large department stores carry petticoats, as do specialty stores, particularly stores which carry bridal fashions.
Women's fashion since at least the 1500s has included a petticoat. Women of all classes would have worn petticoats to inflate their skirts and enhance their privacy, especially in eras where women's underpants were still rare. The petticoat was typically made of a stiff material, so that it would prop up over skirts, or multiple layers of petticoats made from soft fabrics would be worn. The sheer volume of the multiple petticoats would certainly give overskirts more volume, but it was undoubtedly very hot, especially in the summer.
At a minimum, women usually wore at least three petticoats. In some eras, they were designed to be entirely invisible, hidden under the wearer's long skirts. In other instances, the bottom of the petticoat was meant to stick out, and it would be ornamented with lace, ribbons, or embroidery. In other eras, the front of the petticoat was designed to be visible through an open-fronted gown, slits in a dress or skirt, or looped skirts. These petticoats were just as elaborately decorated as the gowns were.
In the twentieth century, the petticoat fell in and out of fashion. At the turn of the century, the slim lines of the Gibson Girl was in fashion, with a long narrow skirt emphasizing a slender body. In the 1940s and 1950s, however, the petticoat returned, in the form of a flounced underskirt in tulle and other stiff fabrics. The use of sturdy, stiff materials meant that women did not need to wear multiple layers of petticoats, although a slip was often worn underneath to reduce itchiness, as the stiff fabrics were usually very scratchy.
Relatives of the petticoat include crinolines, hoop skirts, and bustles. All of these women's undergarments were designed to create a specific shape. Some of them would have been difficult to wear, especially in crowded environments. In the modern era, petticoats are generally worn with formal wear only, when a women can afford to move slowly through a crowded room and when she wants to draw attention to herself. Many popular fashion designers have worked with petticoats, creating lavish full skirts for brides, debutantes, and major social events such as balls and opera openings.