A nucleus which is capable of undergoing fission under the influence of neutrons Uranium-235, an isotope of uranium with mass number 235, is fissionable Plutonium is also fissionable
Having the property of certain atomic nuclei, such as some isotopes of uranium and plutonium, of capturing neutrons and thereupon splitting into two particles with great kinetic energy
capable of undergoing nuclear fission; "a fissionable nucleous"; "fissionable material