# coolant

/ˈkuɫənt/ (US) · /kˈuːlənt/ (UK) · CEFR B2 · Noun

Source: https://englishreference.com/word/coolant
Updated: 2026-05-07

## Definition

a liquid or gas used to keep a machine or engine from getting too hot. You usually find it in cars or large industrial machines.

For teachers: a fluid, typically liquid or gaseous, used to transfer heat away from a mechanical or industrial system to prevent overheating.

## Examples

- The car engine needs more coolant before we drive.
- The mechanic checked the radiator for leaks because the coolant level was dropping too quickly.
- In nuclear reactors, the primary coolant must circulate constantly to absorb thermal energy from the core and prevent a catastrophic meltdown of the fuel rods.

## Usage notes

- Uncountable when referring to the substance generally; countable when referring to specific types or brands of the fluid.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.