a common nonmetallic element belonging to the halogens; best known as a heavy yellow irritating toxic gas; used to purify water and as a bleaching agent and disinfectant; occurs naturally only as a salt (as in sea water)(Freq. 32) • Syn: Cl, atomic number 17 • Derivationally related forms: chlorinate • Hypernyms: chemical element, element, gas, halogen • Hyponyms: radiochlorine • Substance Holonyms: sodium chloride, common salt