If someone is pigheaded, they have already decided, and they will not move, even when a good reason is sitting right in front of them. It is stronger than just stubborn: it has a little heat in it, as if the speaker is tired of arguing. It is not a compliment, but it is not the worst insult either — more like a sigh with an edge. You use it about a person, or about the way they are being just now. It pictures an old idea that a pig will not be pushed. Though actually, real pigs are not always like that; the word is about people, not farm facts. Informal, everyday, a bit blunt.

死腦筋；固執