[ ree-ak-ter ]
/ riˈæk tər /


a person or thing that reacts or undergoes reaction.
Electricity. a device whose primary purpose is to introduce reactance into a circuit.
Immunology, Veterinary Medicine. a patient or animal that reacts positively towards a foreign material.
Also called atomic pile, chain reactor, chain-reacting pile, nuclear reactor, pile. Physics. an apparatus in which a nuclear-fission chain reaction can be initiated, sustained, and controlled, for generating heat or producing useful radiation.
Chemistry. (especially in industry) a large container, as a vat, for processes in which the substances involved undergo a chemical reaction.

Origin of reactor

1885–90; 1940–45 for def 4; react + -or2

Related forms

non·re·ac·tor, noun Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for reactor

British Dictionary definitions for reactor


/ (rɪˈæktə) /


chem a substance, such as a reagent, that undergoes a reaction
short for nuclear reactor
a vessel, esp one in industrial use, in which a chemical reaction takes place
a coil of low resistance and high inductance that introduces reactance into a circuit
med a person sensitive to a particular drug or agent
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012