According to Wikipedia, 

> Moral nihilism (also known as ethical nihilism) is the meta-ethical view that nothing is intrinsically moral or immoral.


> Moral 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?