/ Dictionary / Index C corundum: Meaning and Definition of Find definitions for: co•run•dum Pronunciation: (ku-run'dum), [key] — n. a common mineral, aluminum oxide, AlO, notable for its hardness: transparent varieties, as sapphire and ruby, are used as gems, other varieties as abrasives: often made synthetically. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: corundum (Thesaurus) Coruña coruscant Related Content Daily Word Quiz: agitated Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language