chain reaction Definition

1. physics.
A nuclear reaction that is self-sustaining, eg nuclear fission, in which the splitting of atomic nuclei is accompanied by the release of neutrons, which themselves cause the splitting of more nuclei.
2. chem.
A chemical reaction that is self-sustaining because a change in one molecule causes many other molecules to undergo change, eg during combustion.
3. A series of events, each causing the next.