Synset

a fluid agent (gas or liquid) that produces cooling; especially one used to cool a system by transferring heat away from one part to another
<noun.substance>   freq. cnt.: 2 freq. cnt.: 2

coolant

sample sentences

"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"