DuckCorp Dico

Found one definition

1.                 From WordNet (r) 3.0 (2006):
                   
   
   
                   
                     
   atomic number 61
       n 1: a soft silvery metallic element of the rare earth group
            having no stable isotope; was discovered in radioactive
            form as a fission product of uranium [syn: promethium,
            Pm, atomic number 61]