Coolant is a liquid used to keep a machine or engine cool while it is operating.
英英词典释义
Noun
1. a fluid agent (gas or liquid) that produces cooling; especially one used to cool a system by transfering heat away from one part to another;
"he added more coolant to the car's radiator""the atomic reactor used a gas coolant""lathe operators use an emulsion of oil and water as a coolant for the cutting tool"