DuckCorp Dico

Found one definition

1.                 From WordNet (r) 3.0 (2006):
                   
   
   
                   
                     
   atomic number 17
       n 1: 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) [syn:
            chlorine, Cl, atomic number 17]