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