Home›Browse›N›nictitating membranenictitating membraneOur editors are putting together more complete content — check back in about 20 minutesnictitating membranenictitating membrane — nounnoun1. a transparent inner eyelid in some animals that can be drawn across the eye for 1.nounDefinitiona transparent inner eyelid in some animals that can be drawn across the eye for protectionExampleCats have a nictitating membrane that helps keep their eyes moist.