calcium

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

• noun A silvery, moderately hard alkaline-earth metal that constitutes approximately 3.6 percent of the earth's crust and is a basic component of most animals and plants. It occurs naturally in limestone, gypsum, and fluorite, and its compounds are used to make plaster, quicklime, Portland cement, and metallurgic and electronic materials. Atomic number 20; atomic weight 40.08; melting point 842°C; boiling point 1,484°C; specific gravity 1.54; valence 2. cross-reference: Periodic Table.

from The Century Dictionary.

• noun Chemical symbol, Ca; atomic weight, 40. A metal having a light-yellow color and brilliant luster, about as hard as gold, very ductile, and having a specific gravity of about 1.57.
• noun A calcium light.

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

• noun (Chem.) An elementary substance; a metal which combined with oxygen forms lime. It is of a pale yellow color, tenacious, and malleable. It is a member of the alkaline earth group of elements. Atomic weight 40. Symbol Ca.
• noun an intense light produced by the incandescence of a stick or ball of lime in the flame of a combination of oxygen and hydrogen gases, or of oxygen and coal gas; -- called also Drummond light and lime light.

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

• noun A chemical element, atomic number 20, that is an alkaline earth metal and occurs naturally as carbonate in limestone and as silicate in many rocks.

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

• noun a white metallic element that burns with a brilliant light; the fifth most abundant element in the earth's crust; an important component of most plants and animals