Source : Webster's Revised Unabridged Dictionary (1913)

Hexahedron \Hex`a*he"dron\, n.; pl. E. {Hexahedrons}, L.
   {Hexahedra}. [Hexa- + Gr. ? seat, base, fr. ? to sit: cf. F.
   hexa[`e]dre.] (Geom.)
   A solid body of six sides or faces.

   {Regular hexahedron}, a hexagon having six equal squares for
      its sides; a cube.

Source : WordNet®

hexahedron
     n : any polyhedron having six plane faces