coolant

n. means for cooling, cooling agent (usually a liquid)

A coolant, or heat transfer fluid, is a fluid which flows through a device in order to prevent its overheating, transferring the heat produced by the device to other devices that utilize or dissipate it. An ideal coolant has high thermal capacity, low viscosity, is low-cost, and is chemically inert, neither causing nor promoting corrosion of the cooling system. Some applications also require the coolant to be an electrical insulator.
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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"
(hypernym) fluid
(derivation) cool, chill, cool down

A substance circulated through a nuclear reactor to remove or transfer heat. The most commonly used coolant in the United States is water. Other coolants include heavy water, air, carbon dioxide, helium, liquid sodium, and a sodium-potassium alloy.

ماده خنک کننده
  

Something , some material which freeze or cool down other materials