fis·sion 
/ˈfɪʃn̩/ noun
/ˈfɪʃn̩/ noun [noncount] 1 physics : a process in which the nucleus of a heavy atom is split apart ◊A large amount of energy is released when fission occurs. —called also nuclear fission; — compare fusion 2 biology : a kind of reproduction in which a cell or body divides into two or more parts and each part grows into a whole new individual
