fis·sion (fĭshən, fĭzh-)
1. The act or process of splitting into parts.
2. A nuclear reaction in which an atomic nucleus, especially a heavy nucleus, such as an isotope of uranium, splits into fragments, usually two fragments of comparable but unequal mass along with a few neutrons, releasing energy in the order of magnitude of 100 million electron volts. Nuclear fission may occur spontaneously or may be induced by the absorption of a neutron, which can initiate a nuclear chain reaction.
3. Biology An asexual reproductive process in which a unicellular organism divides into two or more independently maturing daughter cells.
v. fis·sioned, fis·sion·ing, fis·sions
To cause (an atom) to undergo fission.
To undergo fission.
[Latin fissiō, fissiōn-, a cleaving, from fissus, split; see FISSI-.]
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