<chemistry> A light earthy white substance, consisting of magnesium oxide, and obtained by heating magnesium hydrate or carbonate, or by burning magnesium. It has a slightly alkaline reaction, and is used in medicine as a mild antacid laxative. See Magnesium. Magnesia alba [L.

<medicine> A bulky white amorphous substance, consisting of a hydrous basic carbonate of magnesium, and used as a mild cathartic.

Origin: L. Magnesia, fem. Of Magnesius of the country Magnesia, Gr. A magnet. Cf. Magnet.

(01 Mar 1998)