Source : Webster's Revised Unabridged Dictionary (1913)

Mandible \Man"di*ble\, n. [L. mandibula, mandibulum, fr. mandere
   to chew. Cf. {Manger}.]
   1. (Anat.) The bone, or principal bone, of the lower jaw; the
      inferior maxilla; -- also applied to either the upper or
      the lower jaw in the beak of birds.

   2. (Zo["o]l.) The anterior pair of mouth organs of insects,
      crustaceaus, and related animals, whether adapted for
      biting or not. See Illust. of {Diptera}.

Source : WordNet®

mandible
     n : the lower jawbone in vertebrates; it is hinged to open the
         mouth [syn: {lower jaw}, {mandibula}, {mandibular bone},
         {submaxilla}, {lower jawbone}, {jawbone}, {jowl}]