| Noun | 1. | A-bomb - 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)bomb - an explosive device fused to explode under specific conditions clean bomb - an atom bomb leaving little or no radioactive contamination dirty bomb - an atom bomb that leaves considerable radioactive contamination neutron bomb - atom bomb that produces lethal neutrons with less blast atomic weapon, nuclear weapon - a weapon of mass destruction whose explosive power derives from a nuclear reaction plutonium pit, plutonium trigger - a steel or beryllium sphere containing plutonium 239 that triggers nuclear fission when compressed by explosives |