reactor

American  

[ree-ak-ter] / riˈæk tər /

noun

reactors plural

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

Derived Forms

• nonreactor
  noun

Inflected Forms

Nouns

• reactors
  plural

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

With its safety analysis complete, the company confirmed it was on track to achieve first criticality for the Groves nuclear reactor this month.

From Barron's • Jul. 1, 2026

For now, a test reactor is a start.

From Barron's • Jul. 1, 2026

Once authorized, the facility will be allowed to load nuclear fuel and begin start-up testing to achieve first criticality—the point at which a reactor sustains a controlled nuclear chain reaction.

From Barron's • Jul. 1, 2026

The Energy Department will let utilities tap government funds to kick-start reactor orders.

From The Wall Street Journal • Jun. 24, 2026

Triggered by emergency systems, control rods automatically shot up into the reactor cores, putting a damper on the movement of neutrons between the fuel rods.

From "Meltdown" by Deirdre Langeland