a red rag to a bull

a red rag to a bull

A willfully infuriating or aggravating provocation; something that incites great anger or annoyance. An allusion to matadors' practice of waving red flags at a bull during a bullfight, though the color of the flag actually makes no difference to the animal. John's gone to gloat about his success over his brother, which is a red rag to a bull if I've ever seen one. You do realize that bringing your new girlfriend to your ex-wife's house is like a red rag to a bull, right?
See also: bull, rag, red

a red rag to a bull

BRITISH or

a red flag before a bull

AMERICAN
If something always makes a particular person very angry, you can say that it is like a red rag to a bull or a red flag before a bull. This sort of information is like a red rag to a bull for the tobacco companies but it really needs to be exposed. It's a red rag to a bull when my son won't admit that he's wrong. Compare with a red flag.
See also: bull, rag, red