reactor

noun

re·​ac·​tor rē-ˈak-tər 

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

Israel struck the Arak heavy water reactor twice over the last year — in June 2025 and in March 2026. —Benjamin Weinthal, FOXNews.com, 9 May 2026

According to Terrestrial Energy, an IMSR plant has a thermal efficiency of 44 percent and can generate 392 megawatts (MW) of energy from a 884 MW thermal reactor. —Ameya Paleja, Interesting Engineering, 8 May 2026

The Chernobyl reactors are surrounded by a 1,000-square-mile exclusion zone. —Andrea Thompson, Scientific American, 8 May 2026

While there are no modular reactors up and running yet in the United States, Albrecht said some of those in the design phase will use molten salt, helium or liquid metal to help cool the fission process, obviating the need for large amounts of water. —John Aguilar, Denver Post, 7 May 2026

Word History

First Known Use

1890, in the meaning defined at sense 1

Phrases Containing reactor

• atomic reactor
• hyper-reactor
• nuclear reactor

Rhymes for reactor

• acter
• actor
• factor
• tractor
• attractor
• cofactor
• compactor
• contactor
• contractor
• distractor
• extractor
• impactor

Kids Definition

reactor

noun

re·​ac·​tor rē-ˈak-tər 

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 

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)