magnesium oxide n a white highly infusible compound MgO used esp. in refractories, cements, insulation, and fertilizers, in rubber manufacture, and in medicine as an antacid and mild laxative
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[USP] a bulky (light m. oxide) or relatively dense (heavy m. oxide) white powder, MgO; used as a sorbent in pharmaceutical preparations, as an oral antacid and laxative, and as a preventative for hypomagnesemia.Medical dictionary. 2011.