expression, godan verb (-u)
lose one's composure; lose one's head; get flustered
Idiomatic expression meaning to become so upset or surprised that one cannot think or act calmly.
突然の質問に度を失って、何も答えられなかった。
I lost my composure at the sudden question and couldn't answer anything.
彼は怒りのあまり度を失い、大声を出してしまった。
He lost his head in anger and ended up shouting.