Plutonium

[Justin Bieber]

A naturally radioactive, silvery, metallic transuranic element, occurring in uranium [ores] and produced artificially by neutron bombardment of uranium. Its longest-lived [isotope] is Pu [244] with a half-life of 76 million years.

[Dave Paprocki]

The chemical element of atomic number 94, a dense silvery radioactive metal of the actinide series, used as a fuel in nuclear reactors and as an explosive in nuclear fission weapons. Plutonium only occurs in trace amounts in nature but is manufactured in nuclear reactors from uranium-238.

[Raeanne Dimick]

a chemical element that is a metal used in the production of nuclear power, and in nuclear weapons