Material that can be caused to undergo atomic fission when bombarded by neutrons. The most important fissionable materials are uranium-235, plutonium-239, and uranium-233.

Any substance which can be fissioned by neutrons, during which further neutrons are released, e.g. U-235, Pu-239.

Any element containing an isotope with nuclei capable of undergoing fission as a result of interaction with slow neutrons in a nuclear reactor. The two most common examples of such isotopes are uraniu [..]

A nuclide that is capable of undergoing fission after capturing low-energy thermal (slow) neutrons. Although sometimes used as a synonym for fissionable material, this term has acquired its more-restrictive interpretation with the limitation that the nuclide must be fissionable by thermal neutrons. With that interpretation, the three primary fissil [..]

Nuclear material, containing a high proportion of fissile isotopes, which is essential for making nuclear explosives. High-enriched uranium (HEU) and weapons-grade plutonium are examples of fissile ma [..]

A type of fissionable material capable of sustaining a chain reaction by undergoing fission upon the absorption of low-energy (or thermal) neutrons.  Uranium-235, Plutonium-239, and Uranium-233 are th [..]

Any material capable of undergoing fission by thermal (or slow) neutrons. For example, uranium-235 and plutonium-239 are fissile nuclides.

any material in which neutrons can cause a fission reaction. The three primary fissile materials are uranium-233, uranium-235, and plutonium-239.

Although sometimes used as a synonym for fissionable material, this term has acquired a more restricted meaning. Namely, any material that is fissionable by thermal (slow) neutrons. The three primary [..]

Isotopes which can undergo nuclear fission. Example of fissile materials are Uranium-233, uranium-235, plutonium-239, plutonium-241.

 "A type of fissionable material capable of sustaining a chain reaction by undergoing fission upon the absorption of low-energy (or thermal) neutrons.  Uranium-235, Plutonium-239, and Uranium-233 are the most prominently discussed fissile materials for peaceful and nuclear weapons purposes." (NTI)

Fissile materials are capable of undergoing nuclear fission (splitting of the nucleus of an atom) by slow neutrons. Examples of fissile materials are uranium 235 and plutonium 239.

Isotopes which are capable of undergoing nuclear fission. Sometimes the term is restricted to apply only to isotopes which are capable of undergoing fission upon impact with a slow neutron.