The Collaborative International Dictionary of English v.0.48:

Nictitate \Nic"ti*tate\, v. i. [See Nictate.]
   To wink; to nictate.
   [1913 Webster]

   Nictitating membrane (Anat.), a thin membrane, found in
      many animals at the inner angle, or beneath the lower lid,
      of the eye, and capable of being drawn across the eyeball;
      the third eyelid; the haw.
      [1913 Webster]

WordNet (r) 3.0 (2006):

nictitate
    v 1: briefly shut the eyes; "The TV announcer never seems to
         blink" [syn: blink, wink, nictitate, nictate]