/ Dictionary / Index M magnesium arsenate: Meaning and Definition of Find definitions for: magne'sium ar'senate Pronunciation: [key] a white, water-insoluble powder, Mg(AsO)&multiplydot;xHO, used chiefly as an insecticide. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. magnesium magnesium carbonate Related Content Daily Word Quiz: censure Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language