Cách sử dụng
The expression "like waving a red flag in front of a bull" means doing something that is guaranteed to make someone angry or agitated. It comes from the practice of bullfighting, where a red flag (or cape) is used to provoke the bull and make it charge. So, if someone says that doing a particular action is like waving a red flag in front of a bull, it means that it is likely to trigger a negative reaction from someone, just like how a bull will charge at the sight of a red flag.