The Collaborative International Dictionary of English v.0.48:
Rhombohedron \Rhom`bo*he"dron\, n. [NL., fr. Gr. ??? rhomb + ??? seat, base.] (Geom. & Crystallog.) A solid contained by six rhomboids; a parallelopiped. [1913 Webster]WordNet (r) 3.0 (2006):
rhombohedron n 1: a parallelepiped bounded by six similar faces (either rhombuses or parallelograms)