a liquid that boils at below -160 C and is used as a refrigerant
cryogen详细解释
cry.o.gen n.（名词）A liquid, such as liquid nitrogen, that boils at a temperature below about 0 K (-'0=C) and is used to obtain very low temperatures; a refrigerant.致冷剂：一种液体，如液化氮，大约在0K（摄氏-'0度）以下的温度时发生汽化，被用来获取极低的温度；冷冻剂
