- noun a nuclear reaction in which a neutron hits a nucleus, makes it split and so releases further neutrons
- noun a chemical reaction where each stage is started by a chemical substance which reacts with another, producing further substances which can continue to react
- A series of events related in a manner that one initiates or influences the next.
- A reaction which once initiated, continues without additional external influence, usually leading to a great expenditure of energy.
- The bombardment of neutrons upon an unstable nucleus, such as that of uranium, which initiates a sequence of nuclear fissions whose products include other elements, a substantial amount of energy, and more neutrons, which further propagate the reaction. Also called nuclear chain reaction.