A petticoat is an article of clothing worn under a skirt. It helps to smooth out wrinkles in the skirt. In the days when very full skirts were in fashion, a petticoat of several layers helped the skirt stand out. The petticoat has long been a symbol of modesty and proper feminine behavior. It has also been used as an insult towards women who were deemed to be venturing out of proper feminine behavior. For example, Mary Wollstonecraft, an early advocate for women’s rights, was called “a hyena in petticoats.”