nictitating membrane nictitate • nictitation · · · Info · Definitions · Synonyms · Characters · · nictitating membrane · · Text Common · · Latin · · Scripts 20 · · Length 6 · · Syllables Definitions · · · (noun) a protective fold of skin in the eyes of reptiles and birds and some mammals. Synonyms: nictitating membrane, third eyelid. · · Noun Definition 1 Synonyms · · · third eyelid · · Synonym 1 Characters · · space U+0020 a latin small letter a U+0061 b latin small letter b U+0062 c latin small letter c U+0063 e latin small letter e U+0065 g latin small letter g U+0067 i latin small letter i U+0069 m latin small letter m U+006D n latin small letter n U+006E r latin small letter r U+0072 t latin small letter t U+0074