What is another word for concave polyhedron?
Pronunciation: [kɒnkˈe͡ɪv pˌɒlɪhˈiːdɹən] (IPA) 
A concave polyhedron is a three-dimensional geometric shape that has at least one concave or inwardly curving surface. Sometimes referred to as a hollow polyhedron, it is commonly found in nature, including some shells or crystals. There are various synonyms for concave polyhedron, such as caved polyhedron, dented polyhedron, scooped polyhedron, hooked polyhedron or hollow polyhedron. Other terms that can be used interchangeably include indented polyhedron, sunken polyhedron and depressed polyhedron. The variety of synonyms helps describe the shape of a concave polyhedron and emphasize its particular characteristics. Regardless of the term used, this shape can be an intriguing and visually appealing subject for study.
