WordNet (r) 3.0 (2006):

mucous secretion
    n 1: 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 [syn: mucus, mucous secretion]