magnesium oxide

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A white powdery compound, MgO, having a high melting point (2,800°C), used in high-temperature refractories, electrical insulation, food packaging, antacids, cosmetics, and pharmaceuticals.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Chem.) Magnesia.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun inorganic chemistry A white powder (MgO) with a high melting point; it occurs naturally as periclase, an ore of magnesium.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a white solid mineral that occurs naturally as periclase; a source of magnesium