Real Dictionary

nominalism in American English
a philosophical doctrine of the late Middle Ages that all universal or abstract terms are mere necessities of thought or conveniences of language and therefore exist as names only with no ideal realities corresponding to them
noun: the doctrine that general or abstract words do not stand for objectively existing entities and that universals are no more than names assigned to them

nominalism in British English
noun: the philosophical theory that the variety of objects to which a single general word, such as dog, applies have nothing in common but the name