/ Dictionary / Index M magnesite: Meaning and Definition of Find definitions for: mag•ne•site Pronunciation: (mag'nu-sīt"), [key] — n. a mineral, magnesium carbonate, MgCO, having a characteristic conchoidal fracture and usually occurring in white masses. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: magnesite (Thesaurus) magnesia magnesium 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