expression, godan verb (-ru)
lose one's cool; get angry; blow one's top
Idiomatic expression for suddenly becoming very angry, often implying a loss of rational control. Used in informal contexts.
彼はその言葉に頭に血が上って、怒鳴り始めた。
He lost his cool at those words and started shouting.
頭に血が上ると、何を言うかわからない。
When I blow my top, I don't know what I might say.