Cách sử dụng
The expression "a red rag to a bull" means something that is likely to make someone very angry or irritated. It comes from the fact that bulls are often very agitated by the color red, and so if you show them a red rag, it is likely to make them charge at you. This expression is often used to describe situations where someone is likely to get very upset or angry, or when someone is purposely trying to provoke someone else. For example, if you know that your friend gets upset whenever someone mentions politics, you might say that talking about politics is like "a red rag to a bull" for them.