He lost his cool when the computer crashed.

lost 是动词 lose 的过去式，意思是"失去"。 his 是代词 he 的所有格形式，意思是"他的"。 cool 在这里是名词，本意是"凉爽"，引申为"冷静、镇定"的状态。 lost his cool 是一个固定搭配，意思是"失去冷静、发脾气"。