A supremacist is someone who believes their own race, religion, or group is naturally superior to others and should therefore rule over them. In practice the word is almost always preceded by the group in question — *white supremacist* is by far the commonest, and for many readers the word alone now calls that phrase to mind. It is a strongly negative label: nobody is described as a supremacist approvingly, and to call a person one in print is a serious charge, close to calling them a racist with a political programme. That last part matters — the word suggests not just prejudice in the heart but a belief about who ought to hold power, which is why it turns up in reporting about political movements and violence. It also works as an adjective ("supremacist groups", "supremacist ideology").