Source : Webster's Revised Unabridged Dictionary (1913)

Polyhedron \Pol`y*he"dron\, n.; pl. E. {Polyhedrons}., L.
   {Polyhedra}. [NL., fr. Gr. ? with many seats or sides; poly`s
   many + ? a seat or side: cf. F. poly[`e]dre.]
   1. (Geom.) A body or solid contained by many sides or planes.

   2. (Opt.) A polyscope, or multiplying glass.

Source : WordNet®

polyhedron
     n : a solid figure bounded by plane polygons or faces
     [also: {polyhedra} (pl)]

polyhedra
     See {polyhedron}