The Collaborative International Dictionary of English v.0.48:

Anhydride \An*hy"dride\, n. [See Anhydrous.] (Chem.)
   An oxide of a nonmetallic body or an organic radical, capable
   of forming an acid by uniting with the elements of water; --
   so called because it may be formed from an acid by the
   abstraction of water.
   [1913 Webster]

WordNet (r) 3.0 (2006):

anhydride
    n 1: a compound formed from one or more other compounds in a
         reaction resulting in removal of water