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.
Reaching the Sun’s core temperature alone would therefore fall short of what many reactor designs require. — Atharva Gosavi, Interesting Engineering, 31 Oct. 2026 Rosatom wants to bring nuclear power to that market, saying 38 of Africa’s 54 countries have coastlines suitable for its floating reactors. — Ruben Nyanguila, semafor.com, 30 Oct. 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

Phrases Containing reactor

Rhymes for reactor

See All Rhymes for reactor

Browse Nearby Words

reactology
reactor
reactualization
See all Nearby Words

Cite this Entry

“Reactor.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/reactor. Accessed 1 Nov. 2026.

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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)

More from Merriam-Webster on reactor

Britannica.com: Encyclopedia article about reactor

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