/ Dictionary / Index R rhesus: Meaning and Definition of Find definitions for: rhe•sus Pronunciation: (rē'sus), [key] — n. a macaque, Macaca mulatta, of India, used in experimental medicine. See illus. under Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: rhesus (Thesaurus) rheotropism Rhesus factor Related Content Daily Word Quiz: panacea Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language