noun
antifreeze; antifreezing agent
Technical term for a substance added to a liquid to lower its freezing point, used in engines, cooling systems, etc.
冬は車のラジエーターに不凍剤を入れる必要がある。
In winter, you need to put antifreeze in the car's radiator.
Compound of 不 (non-) + 凍 (freeze) + 剤 (agent).