protective secretion of the mucous membranes; in the gut it lubricates the passage of food and protects the epithelial cells; in the nose and throat and lungs it can make it difficult for bacteria to penetrate the body through the epithelium
the white part of an egg; the nutritive and protective gelatinous substance surrounding the yolk consisting mainly of albumin dissolved in water; "she separated the whites from the yolks of several eggs"