The Collaborative International Dictionary of English v.0.48:

Cornea \Cor"ne*a\ (k?r"n?-?), n.; pl. Corneas (-?z). [Fem.
   sing., fr. L. corneus horny, fr. cornu a horn. See Horn.]
   (Anat.)
   The transparent part of the coat of the eyeball which covers
   the iris and pupil and admits light to the interior. See
   Eye.
   [1913 Webster]

WordNet (r) 3.0 (2006):

cornea
    n 1: the transparent dome-shaped anterior portion of the outer
         covering of the eye; it covers the iris and pupil and is
         continuous with the sclera