1. a highly unstable radioactive element (the heaviest of the halogen series); a decay product of uranium and thorium; [syn: astatine, At, atomic number 85]
WordNet (r) 3.0 (2006):
atomic number 85
n 1: a highly unstable radioactive element (the heaviest of the
halogen series); a decay product of uranium and thorium
[syn: astatine, At, atomic number 85]