Magnesia \Mag*ne"si*a\ (?; 277), n. [L. Magnesia, fem. of Magnesius of the country Magnesia, Gr. ? ? ? a magnet. Cf. Magnet.]

(Chem.) 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.]

(Med. Chem.), a bulky white amorphous substance, consisting of a hydrous basic carbonate of magnesium, and used as a mild cathartic.

Source: Webster's Revised Unabridged Dictionary (1913)