Calomel \Cal"o*mel\, n. [Gr. ????? beautiful + ????? black. So called from its being white, though made from a black mixture of mercury and corrosive sublimate. Cf. F. calom['e]las.] (Chem.) Mild chloride of mercury, {Hg2Cl2}, a heavy, white or yellowish white substance, insoluble and tasteless, much used in medicine as a mercurial and purgative; mercurous chloride. It occurs native as the mineral horn quicksilver.