| Noun | 1. | calcium - 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 animalsmetal, metallic element - any of several chemical elements that are usually shiny solids that conduct heat or electricity and can be formed into sheets etc. fluor, fluorite, fluorspar - a soft mineral (calcium fluoride) that is fluorescent in ultraviolet light; chief source of fluorine gypsum - a common white or colorless mineral (hydrated calcium sulphate) used to make cements and plasters (especially plaster of Paris) limestone - a sedimentary rock consisting mainly of calcium that was deposited by the remains of marine animals | |