n. 1 Chem. a silvery-white heavy liquid metallic element occurring naturally in cinnabar and used in barometers, thermometers, and amalgams; quicksilver. °Symb.: Hg. 2 (Mercury) the planet nearest to the sun. 3 any plant of the genus Mercurialis, esp. M. perenne. mercury vapour lamp a lamp in which light is produced by an electric discharge through mercury vapour. mercuric adj. mercurous adj.
[ ME f. L Mercurius messenger of the gods and god of traders f. merx mercis merchandise ]