Definition: A mixture of water and antifreeze (ethylene glycol) which lowers the freezing point of the water in the cooling system, prevents rust and corrosion, lubricates the water pump, and picks up heat from the engine, transferring it to the air passing through the radiator.

Related Resources:

Cooling Systems: Part 1
How this important system works and helps your engine keep its cool.

Cooling Systems: Part 2
How this important system works and helps your engine keep its cool.

Antifreeze: Red or Green
Dexcool® or regular antifreeze? Which antifreeze to use and why.