be like a red rag to a bull to be certain to produce an angry or violent reaction 令人火冒三丈;使人极其恼怒;令人产生激烈的反应 red rag 对于bull来讲就像是个刺激源，可以起到激怒别人做出负面反应的作用。 Don't tell him you support Manchester United - it's like a red rag to a bull!