fis ‧ sion /ˈfɪʃ ə n/ BrE AmE noun [uncountable] technical
[ Date: 1600-1700 ; Language: Latin ; Origin: fissus , past participle of findere 'to split' ]
1 . the process of splitting an atom to produce large amounts of energy or an explosion ⇨ fusion
2 . the process of dividing a cell into two or more parts