A nuclide capable of undergoing fission by interaction with slow neutrons, provided the effective neutron production cross, , exceeds the effective absorption cross section .
For a discussion of the terms fissile, fissionable and fissible see the article by Kelley and Clayton, 1985.
Glossary of terms in nuclear science, American Nuclear Society.
R. E. Kelley and E. D. Clayton, Nucl. Sci. Eng., 91, 481 (1985)