maxilla

from WordNet (r) 3.0 (2006)

maxilla
    n 1: the jaw in vertebrates that is fused to the cranium [syn:
         {upper jaw}, {upper jawbone}, {maxilla}, {maxillary}]

from The Collaborative International Dictionary of English v.0.48

Maxilla \Max*il"la\, n.; pl. {Maxillae}. [L., dim. of mala jaw,
   jawbone.]
   1. (Anat.)
      (a) The bone of either the upper or the under jaw.
      (b) The bone, or principal bone, of the upper jaw, the
          bone of the lower jaw being the mandible. [Now
          commonly used in this restricted sense.]
          [1913 Webster]

   2. (Zool.) One of the lower or outer jaws of arthropods.
      [1913 Webster]

   Note: There are usually two pairs in Crustacea and one pair
         in insects. In certain insects they are not used as
         jaws, but may form suctorial organs. See Illust. under
         {Lepidoptera}, and {Diptera}.
         [1913 Webster] Maxillar