Source : Webster's Revised Unabridged Dictionary (1913)

Decahedron \Dec`a*he"dron\, n.; pl. E. {Decahedrons}, L.
   {Decahedra}. [Pref. deca- + Gr. 'e`dra a seat, a base, fr.
   'e`zesthai to sit: cf. F. d['e]ca[`e]dre.] (Geom.)
   A solid figure or body inclosed by ten plane surfaces.
   [Written also, less correctly, {decaedron}.]

Source : WordNet®

decahedron
     n : any polyhedron having ten plane faces