/ Dictionary / Index M magnesium oxide: Meaning and Definition of Find definitions for: magne'sium ox'ide Pronunciation: [key] magnesia. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. magnesium light magnesium peroxide Related Content Daily Word Quiz: gregarious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language