reactor

American  

[ree-ak-ter] / riˈæk tər /

noun

1. a person or thing that reacts or undergoes reaction.

2. Electricity. a device whose primary purpose is to introduce reactance into a circuit.

3. Immunology, Veterinary Medicine. a patient or animal that reacts positively towards a foreign material.

4. Physics. nuclear reactor.

5. Chemistry. (especially in industry) a large container, as a vat, for processes in which the substances involved undergo a chemical reaction.

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reactor British  

/ rɪˈæktə /

noun

1. chem a substance, such as a reagent, that undergoes a reaction

2. short for nuclear reactor

3. a vessel, esp one in industrial use, in which a chemical reaction takes place

4. a coil of low resistance and high inductance that introduces reactance into a circuit

5. med a person sensitive to a particular drug or agent

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Other Word Forms

• nonreactor noun

Etymology

Origin of reactor

First recorded in 1885–90; 1940–45 reactor for def. 4; react + -or ²

Example Sentences

Tehran then turned to Russia, which took over the contract in January 1995, aiming to commission the 1,000-megawatt pressurized water reactor in 1999.

From Barron's • Apr. 4, 2026

Not everyone is fully on board, however — including Isaacman, whose ambitious plans involve developing a lunar nuclear reactor by 2030.

From MarketWatch • Mar. 31, 2026

Dan Eggers, Constellation’s senior vice president for finance, told Barron’s last week that any new reactor investments would have to clear a high bar.

From Barron's • Mar. 30, 2026

They raised funds by showing investors a $10,000 research reactor constructed from fiberglass sewer pipe wrapped in speaker wire.

From The Wall Street Journal • Mar. 28, 2026

When pressure in the reactor gets too high, a safety valve opens and allows steam to escape into the torus, where it condenses back into water.

From "Meltdown" by Deirdre Langeland