Source : Webster's Revised Unabridged Dictionary (1913)

Eyelid \Eye`lid"\, n. (Anat.)
   The cover of the eye; that portion of movable skin with which
   an animal covers or uncovers the eyeball at pleasure.

Source : WordNet®

eyelid
     n : either of two folds of skin that can be moved to cover or
         open the eye; "his lids would stay open no longer" [syn:
         {lid}, {palpebra}]