calcium oxide

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

• noun A white, caustic, lumpy powder, CaO, used as a refractory, as a flux, in glassmaking, in waste treatment, in insecticides, as an industrial alkali, and in manufacturing steel, paper, and building materials.

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

• noun inorganic chemistry A white powderous substance, CaO, commonly known as lime or quicklime; normally made by heating calcium carbonate.

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

• noun a white crystalline oxide used in the production of calcium hydroxide