Source : Webster's Revised Unabridged Dictionary (1913)

Prognathous \Prog"na*thous\, a. [Gr. ? before + ? the jaw]
   (Anat.)
   Having the jaws projecting beyond the upper part of the face;
   -- opposed to orthognathous. See {Gnathic index}, under
   {Gnathic}.

         Their countenances had the true prognathous character.
                                                  --Kane.

Source : WordNet®

prognathous
     adj : having a projecting lower jaw [syn: {prognathic}, {hypognathous}]
           [ant: {opisthognathous}]