Definition of third eyelid in English:

Share this entry

third eyelid


Informal term for nictitating membrane.
Example sentences
  • Crocodilians' eyes are immobile spheres covered by three eyelids: the third eyelid, the nictitating membrane, is transparent, but protects the eye from water.
  • Eversion of the nictitating membrane is a condition in which the third eyelid protrudes.
  • These membranes, essentially a third eyelid, can cover the exposed portion of the eye, since, as in all sharks, the upper and lower eyelids of catsharks cannot completely cover the eyeball.

For editors and proofreaders

Syllabification: third eye·lid

Share this entry

What do you find interesting about this word or phrase?

Comments that don't adhere to our Community Guidelines may be moderated or removed.