noun.
The transparent convex anterior portion of the outer fibrous coat of the eyeball that covers the iris and the pupil and is continuous with the sclera.
The Century Dictionary and Cyclopedia
noun.
The firm, transparent anterior portion of the eyeball.
noun.
In entomology, the outer surface of an insect's compound eye.
the GNU version of the Collaborative International Dictionary of English
noun.
The transparent part of the coat of the eyeball which covers the iris and pupil and admits light to the interior. See eye.