The Collaborative International Dictionary of English v.0.48:
parallelepiped \parallelepiped\ n. (Geometry) A prism whose bases are parallelograms. Syn: parallelopiped, parallelepipedon, parallelopipedon. [WordNet 1.5]WordNet (r) 3.0 (2006):
parallelepiped n 1: a prism whose bases are parallelograms [syn: parallelepiped, parallelopiped, parallelepipedon, parallelopipedon]