a silvery soft waxy metallic element of the alkali metal group; occurs abundantly in natural compounds (especially in salt water); burns with a yellow flame and reacts violently in water; occurs in sea water and in the mineral halite (rock salt) • Syn: sodium, atomic number 11 • Hypernyms: metallic element, metal • Substance Holonyms: seawater, saltwater, brine, halite, rock salt