What is "prismatoid"

n. (context mathematics English) Any polyhedron whose vertex all lie in either of two parallel planes

n. a polyhedron whose vertices all lie in one or the other of two parallel planes; the faces that lie in those planes are the bases of the prismatoid

In geometry, a prismatoid is a polyhedron where all vertices lie in two parallel planes. Its lateral faces can be trapezoids or triangles. If both planes have the same number of vertices, and the lateral faces are either parallelograms or trapezoids, it is called a prismoid.