a white, soft, caustic solid, CaO, prepared by heating calcium carbonate; lime: used in making mortar and plaster, in ceramics, etc.
See calcium oxide in American Heritage Dictionary 4
noun
A white, caustic, lumpy powder, CaO, used as a refractory, as a flux, in manufacturing steel and paper, in glassmaking, in waste treatment, in insecticides, and as an industrial alkali. Also called lime3.