According to Wikipedia,
Moral nihilismMoral nihilism (also known as ethical nihilism) is the meta-ethical view that nothing is intrinsically moral or immoral.
Moral realismMoral realism (also ethical realism) is the position that ethical sentences express propositions that refer to objective features of the world.
So, as far as I understand, these are two opposite views in moral philosophy, the first of which argues that there are no moral facts/properties, whereas the second that there are such things.
But I think it is obvious that before asking "Does X exists?" one should provide an exact definition of "X", so I guess that those who engage in this nihilism/realism debate agree on the definition of "moral fact/property".
Therefore my question is, What is this definition?