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]
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]