nu·cle·ar fis·sion
noun/ˌnjuːkliə ˈfɪʃn/
/ˌnuːkliər ˈfɪʃn/
(also fission)
[uncountable] (physics)- the act or process of splitting the nucleus (= central part) of an atom, when a large amount of energy is released
（核）裂变，分裂