coolant

American  

[koo-luhnt] / ˈku lənt /

noun

1. a substance, usually a liquid or a gas, used to reduce the temperature of a system below a specified value by conducting away the heat produced in the operation of the system, as the liquid in an automobile cooling system or the fluid that removes heat from the core of a nuclear reactor.

2. a lubricant that dissipates the heat caused by friction.

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coolant British  

/ ˈkuːlənt /

noun

1. a fluid used to cool a system or to transfer heat from one part of it to another

2. a liquid, such as an emulsion of oil, water, and soft soap, used to lubricate and cool the workpiece and cutting tool during machining

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Etymology

Origin of coolant

First recorded in 1925–30; cool + -ant

Example Sentences

While most people might be familiar with helium as a filler for balloons, the gas is used as a coolant, including in semiconductor manufacturing and MRI machines.

From Salon • Mar. 30, 2026

Most Americans think of helium as the gas that holds balloons aloft, but, more important, it is an essential coolant in MRI machines and semiconductor manufacturing.

From The Wall Street Journal • Mar. 28, 2026

Sales of its Opteon coolant, which can be used in data centers, grew 37% to $243 million, but it wasn’t enough to offset an earnings miss.

From Barron's • Feb. 20, 2026

Chillers circulate water or another coolant through pipes to absorb heat, then transfer it to a cooling tower or other system to remove it.

From MarketWatch • Jan. 8, 2026

Rods remain submerged in the coolant and radiation shield of the water while they are being moved.

From "Meltdown" by Deirdre Langeland