Definitions for "Fissionable Material"
Any material readily fissioned by slow neutrons, for example, uranium 235 and plutonium 239.
Material whose atoms are easily split when struck by neutrons, and that can easily sustain either a controlled or explosive chain reaction, depending on concentration and other conditions of use; also commonly referred to as a "fissile" material.
A material that can be fissioned (split) into other nuclei by any process.