An Etymological Dictionary of Astronomy and Astrophysics

Any material that is capable of undergoing → nuclear fission by → thermal neutrons. 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.

Etymology (EN): From L. fissilis, from fiss(us), + -illis a suffix of adjectives expressing capability, susceptibility, liability, aptitude, etc.

Etymology (PE): Šekâftani, from šekâft, → fission + -i a suffix expressing capability, aptitude, etc.