Definition of third eyelid in English:

third eyelid

Syllabification: third eye·lid

noun

Informal term for nictitating membrane.
More 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.

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Word of the day nous
Pronunciation: naʊs
noun
common sense; practical intelligence