(n) 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, Syn. atomic number 94, Pu
(n) a highly fissionable isotope of plutonium that is used in atomic weapons and as a reactor fuel; produced by irradiating uranium 238 with slow electrons
(n) a nuclear weapon in which enormous energy is released by nuclear fission (splitting the nuclei of a heavy element like uranium 235 or plutonium 239), Syn. plutonium bomb, atomic bomb, A-bomb, fission bomb