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

Explanation

A reactor is where a nuclear reaction is controlled, making it possible to create energy or any number of artificial elements. Reactor these days almost always refers to a nuclear reactor, where atomic fission of uranium or plutonium creates the heat used to make steam to generate electricity. Originally, though, reactor meant a vessel in which chemical processes were made to generate useful products such as nylon and artificial sweetener. These reactors are still used in chemical manufacturing plants.

Example Sentences

Among several approaches, the road map pointed to a unique reactor concept — field-reversed configurations, “which could significantly reduce the cost of fusion power.”

From MarketWatch • May 18, 2026

The UAE said the reactor was not affected and the plant was operating as normal.

From MarketWatch • May 17, 2026

NextEra and Google in October announced a deal to restart a NextEra nuclear reactor in Iowa.

From The Wall Street Journal • May 16, 2026

The winners of the new grants include Constellation Energy, the country’s largest nuclear reactor owner.

From Barron's • May 14, 2026

In the building housing reactor 3, a crane operator was stuck in the cockpit of his crane.

From "Meltdown" by Deirdre Langeland