n. & v.
--n.
1. Physics the spontaneous or impact-induced splitting of a heavy atomic nucleus, accompanied by a release of energy.
2 Biol. the division of a cell etc. into new cells etc. as a mode of reproduction.
--v.intr. & tr. undergo or cause to undergo fission.
Phrases and idioms:
fission bomb an atomic bomb.
Derivatives:
fissionable adj.
Etymology: L fissio (as FISSURE)