- coolant - 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"
--1 is a kind of fluid; agent
Derived forms: verb cool1, verb cool2