瞬膜

[ noun ]
a protective fold of skin in the eyes of reptiles and birds and some mammals
<noun.body>

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

{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.