The term "racist" used to mean someone who believed that one's race, or ethnic background was superior to another's. It was a form of belief in racial supremacy.

It didn't mean that someone used race as a form of prejudice. But for decades this hasn't been the case, and it is almost exclusively used to describe someone who uses prejudice or discriminates others on the basis of race or ethnicity.

And now we no longer have a colloquial or formal single word for someone who holds racial supremacist views, because the two ideas have commingled.