mucus - 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 epitheliumsecretion - a functionally specialized substance (especially one that is not a waste) released from a gland or cell sputum, phlegm - expectorated matter; saliva mixed with discharges from the respiratory passages; in ancient and medieval physiology it was believed to cause sluggishness leucorrhea, leukorrhea - discharge of white mucous material from the vagina; often an indication of infection mucin - a nitrogenous substance found in mucous secretions; a lubricant that protects body surfaces |