Poppins Box is a term to describe female genitalia. This term makes reference to the movie Mary Poppins who carries around a bag of infinite internal proportions. She is seen removing an entire coat rack amongst other large items from her bag.

This definition is etremely useful when referring to a woman with a seemingly large, deep, or otherwise spacious vagina.

When you eat dirt for the first time and leave your family to build a shack in the woods