re·ac·tor | \ rē-ˈak-tər \

Definition of reactor 

1 : one that reacts

2 : a device (such as a coil, winding, or conductor of small resistance) used to introduce reactance into an alternating-current circuit

3a : a vat for an industrial chemical reaction

b : a device for the controlled release of nuclear energy (as for producing heat)

Examples of reactor in a Sentence

Recent Examples on the Web

He was also shown the beginnings of a light-water reactor that could produce more plutonium. The Economist, "North Korea presents nuclear disarmament’s biggest challenge yet," 5 July 2018 But under the deal, the regime froze its nuclear activities and agreed to dismantle nuclear facilities in return for oil and two light-water nuclear reactors for electricity. John Hudson,, "'The most watered-down joint statement ... ever': Past presidents extracted more concessions from North Korea, experts say," 12 June 2018 In return, Tehran limited its ability to enrich uranium, reconfigured a heavy-water reactor to block it from producing plutonium, drastically reduced its uranium stockpile and agreed to international inspections and monitoring. Tracy Wilkinson,, "Trump pulls U.S. out of Iran nuclear deal and announces sweeping new economic sanctions," 8 May 2018 Radioactive Response Humans still can't locate the hundreds of tons of fuel inside the nuclear reactors that suffered meltdowns in 2011—but maybe robots can. Vince Beiser, WIRED, "Fukushima’s Other Big Problem: A Million Tons of Radioactive Water," 27 Apr. 2018 Images also showed the testing of a nuclear-reactor cooling system at Yongbyon. Tracy Wilkinson,, "North Korea accuses U.S. of making 'unilateral' demands in nuclear talks," 7 July 2018 Maps of neutrinos emanating from the surface of the Earth have even been used to identify the sites of nuclear reactors. Author: Sarah Kaplan, Anchorage Daily News, "In a cosmic first, scientists detect ‘ghost particles’ from a distant galaxy," 12 July 2018 Maps of neutrinos emanating from the surface of the Earth have even been used to identify the sites of nuclear reactors. Sarah Kaplan,, "In a cosmic first, scientists detect 'ghost particles' from a distant galaxy," 12 July 2018 The stockpile results from technical challenges in achieving fuel recycling and from slow restarts of reactors to burn it amid widespread anti-nuclear sentiment. Mari Yamaguchi, The Seattle Times, "Japan OKs ambitious nuke energy goals, plutonium reuse plan," 3 July 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'reactor.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of reactor

1890, in the meaning defined at sense 1

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Phrases Related to reactor

nuclear reactor

Statistics for reactor

Last Updated

10 Sep 2018

Look-up Popularity

Time Traveler for reactor

The first known use of reactor was in 1890

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More Definitions for reactor



English Language Learners Definition of reactor

physics : a large device that produces nuclear energy


re·ac·tor | \ rē-ˈak-tər \

Kids Definition of reactor

: a device using atomic energy to produce heat


re·ac·tor | \ rē-ˈak-tər \

Medical Definition of reactor 

1 : one that reacts: as

a : a chemical reagent

b : an individual reacting to a stimulus

c : an individual reacting positively to a foreign substance (as in a test for disease) reactors to tuberculin

2a : a piece of equipment in which a chemical reaction and especially an industrial chemical reaction is carried out

b : a device for the controlled release of nuclear energy (as for producing heat)

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Comments on reactor

What made you want to look up reactor? Please tell us where you read or heard it (including the quote, if possible).


the setting in which something occurs

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