Breadcrumb Home > Dictionary > Index M mucin: Meaning and Definition of Find definitions for: mu•cin Pronunciation: (my'sin), [key] — n. Biochem. any of a class of glycoproteins found in saliva, gastric juice, etc., that form viscous solutions and act as lubricants or protectants on external and internal surfaces of the body. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: mucin (Thesaurus) mucilaginous muciparous ✖ Related Content Daily Word Quiz: supercilious Analogy of the Day: Today’s Analogy Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language