"fission" in the noun sense
reproduction of some unicellular organisms by division of the cell into two more or less equal parts
2. fission, nuclear fission
a nuclear reaction in which a massive nucleus splits into smaller nuclei with the simultaneous release of energy
Source: WordNet® (An amazing lexical database of English)
Princeton University "About WordNet®."
WordNet®. Princeton University. 2010.
View WordNet® License