A petticoat is an undergarment that women and girls wore beneath their skirts or dresses, particularly in the 1800s and early 1900s. Think of it as a skirt worn under another skirt. Petticoats helped dresses hold their shape and made them look fuller and more elegant, especially the fancy ball gowns you see in period movies or paintings.

In the mid-1800s, some petticoats were enormous, supported by hoops made of wire or whalebone, creating those dramatic bell-shaped skirts that could barely fit through doorways. By the late 1800s, petticoats helped create the fashionable bustle effect, where skirts puffed out dramatically in the back.

While most modern clothing doesn't require petticoats, you might still see them under formal dresses, wedding gowns, or historical costumes. Square dancers and some traditional folk dancers wear petticoats to make their skirts swirl and bounce during performances.

When reading historical novels set in the 1800s or early 1900s, you'll encounter petticoats constantly because they were an essential part of everyday clothing for women and girls during those years.