/ Dictionary / Index R rheum: Meaning and Definition of Find definitions for: rheum Pronunciation: (rm), [key] a thin discharge of the mucous membranes, esp. during a cold. catarrh; cold. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: rheum (Thesaurus) rhetorician rheumatic Related Content Daily Word Quiz: placid Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language