Plutonium

[pluː'təʊnɪəm] or [plu'tonɪəm]

Definition

(noun.) a solid silvery grey radioactive transuranic element whose atoms can be split when bombarded with neutrons; found in minute quantities in uranium ores but is usually synthesized in nuclear reactors; 13 isotopes are known with the most important being plutonium 239.

Typist: Yvette--From WordNet