chain reaction

WordReference Random House Learner's Dictionary of American English © 2026

ˈchain reˌac•tion, n. [countable]

1. Physics a reaction in which the substance produced in one reaction causes additional reactions:
   a nuclear chain reaction.
2. a series of events in which each event is the result of the one coming before it, and the cause of the one following it.

WordReference Random House Unabridged Dictionary of American English © 2026

chain′ reac′tion, 

1. Physics a self-sustaining reaction in which the fission of nuclei of one generation of nuclei produces particles that cause the fission of at least an equal number of nuclei of the succeeding generation.
2. Chemistry a reaction that results in a product necessary for the continuance of the reaction.
3. a series of events in which each event is the result of the one preceding and the cause of the one following.
• 1925–30

Collins Concise English Dictionary © HarperCollins Publishers::

chain reaction noun

1. a process in which a neutron colliding with an atomic nucleus causes fission and the ejection of one or more other neutrons, which induce other nuclei to split
2. a chemical reaction in which the product of one step is a reactant in the following step
3. a series of rapidly occurring events, each of which precipitates the next