Coolant (noun)

A substance used to reduce or regulate the temperature of a system, especially in an engine or reactor.

Origin:

Mid 19th century. from cool + -ant.

Examples:

1. The coolant was added to the engine to prevent overheating.
2. The coolant level was checked regularly to ensure proper operation of the system.
3. The coolant was a mixture of water and antifreeze.
4. The coolant flowed through the engine to remove heat.
5. The coolant temperature was monitored to avoid engine damage.