nictitating membrane

American  

[nik-ti-tey-ting mem-breyn] / ˈnɪk tɪˌteɪ tɪŋ ˈmɛm breɪn /

noun

1. a thin membrane, or inner or third eyelid, present in many animals, capable of being drawn across the eyeball, as for protection.

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nictitating membrane British  

/ ˈnɪktɪˌteɪtɪŋ /

noun

1. Also called: third eyelid.   haw.  (in reptiles, birds, and some mammals) a thin fold of skin beneath the eyelid that can be drawn across the eye

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nictitating membrane Scientific  

/ nĭk′tĭ-tā′tĭng /

1. A transparent inner eyelid in birds, reptiles, amphibians, and some mammals that protects and moistens the eye without blocking vision.

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Etymology

Origin of nictitating membrane

1705–15; nictitate ( def. ) + -ing ²

Example Sentences

Separately, the sclera, the eye’s outer layer, would most closely resemble those of horses and cows and include a nictitating membrane, the built-in goggles that make it possible to see underwater.

From New York Times • Dec. 30, 2022

In her 2018 special “Elder Millennial,” she references a nictitating membrane, the translucent inner eyelid typically found in reptiles and birds.

From Los Angeles Times • Oct. 10, 2022

The patterns and colors of the creature's fins, shell and wrinkled neck are exquisitely rendered, as is the dull sheen of its left eye's nictitating membrane.

From Seattle Times • Dec. 30, 2010

A nictitating membrane lowered itself over her eyes.

From "Middlesex: A Novel" by Jeffrey Eugenides

Our craniote ancestors had a third eye-lid, the nictitating membrane, which was drawn over the eye from its inner angle.

From The Evolution of Man — Volume 2 by Haeckel, Ernst Heinrich Philipp August