(noun) protective secretion of the mucus 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
Definitions for Yolk
(noun) nutritive material of an ovum stored for the nutrition of an embryo (especially the yellow mass of a bird or reptile egg)
(noun) the yellow spherical part of an egg that is surrounded by the albumen