reactor

noun

re·​ac·​tor rē-ˈak-tər How to pronounce reactor (audio)
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
3
a
: 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
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
Kronos micro nuclear reactor for practical applications NANO Nuclear focuses on creating scalable reactors for practical applications. Aman Tripathi, Interesting Engineering, 3 Apr. 2026 According to a 2024 study, of 204 reactors that have been closed, only 11 plants with a capacity over 100 megawatts have been fully decommissioned, and 200 more reactors will reach the end of their lifetimes in the next 20 years. Katherine Bourzac, IEEE Spectrum, 2 Apr. 2026 Commercial reactors typically require uranium enriched to less than 5%, while research reactors used for testing or medicine generally require uranium enriched to up to 20%. Harmeet Kaur, CNN Money, 1 Apr. 2026 SMRs are reactors of up to 300 MW per unit, which are about one-third the size of conventional large reactors. Angelica Ang, Fortune, 1 Apr. 2026 See All Example Sentences for reactor

Word History

First Known Use

1890, in the meaning defined at sense 1

Time Traveler
The first known use of reactor was in 1890

Browse Nearby Words

Cite this Entry

“Reactor.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/reactor. Accessed 5 Apr. 2026.

Kids Definition

reactor

noun
re·​ac·​tor rē-ˈak-tər How to pronounce reactor (audio)
1
: one that reacts
2
: a device for the controlled release of nuclear energy (as for producing heat)

Medical Definition

reactor

noun
re·​ac·​tor rē-ˈak-tər How to pronounce reactor (audio)
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
2
a
: 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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