1) nuclear fission
2) fission
the division of a heavy nucleus into two or, rarely, more parts with masses of equal order of magnitude, usually accompanied by the emission of neutrons, gamma rays and, rarely, small charged nuclear fragments
GRM: n.(1,2)
References:
GEN nuclear reaction
SPE spontaneous fission
SPE thermal neutron fission
SPE thermal fission
SPE ternary fission
SPE photofission
SPE fast fission
SPE tripartition

ENERGY TERM COURTESY OF ENERGY.EU