The Collaborative International Dictionary of English v.0.48:

Dodecahedron \Do*dec`a*he"dron\, n. [Gr. ?; ? twelve + ? seat,
   bottom, base: cf. F. dod['e]ca[`e]dre.] (Geom. & Crystallog.)
   A solid having twelve faces.
   [1913 Webster]

   Note: The regular dodecahedron is bounded by twelve equal and
         regular pentagons; the pyritohedron (see
         Pyritohedron) is related to it; the rhombic
         dodecahedron is bounded by twelve equal rhombic faces.
         [1913 Webster]

WordNet (r) 3.0 (2006):

dodecahedron
    n 1: any polyhedron having twelve plane faces