The Collaborative International Dictionary of English v.0.48:

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.
      [1913 Webster]

   2. (Zool.) The anterior pair of mouth organs of insects,
      crustaceaus, and related animals, whether adapted for
      biting or not. See Illust. of Diptera.
      [1913 Webster]

WordNet (r) 3.0 (2006):

mandible
    n 1: the jaw in vertebrates that is hinged to open the mouth
         [syn: lower jaw, mandible, mandibula, mandibular
         bone, submaxilla, lower jawbone, jawbone, jowl]