Noun | 1. | protective fold - a flap of tissue that protects what it covers eyelid, lid, palpebra - either of two folds of skin that can be moved to cover or open the eye; "his lids would stay open no longer" nictitating membrane, third eyelid - a protective fold of skin in the eyes of reptiles and birds and some mammals flap - a movable piece of tissue partly connected to the body |