In more general terms, a nomic is something that is generally valid, sometimes to the extent of being a law of nature. 'Nomic' may mean 'ordinary', 'conventional', or 'guaranteed'.
In my limited experience with it used in a philosophical context it is used to mean guaranteed via the laws of nature.
Also:
Relating to a musical nome, that is, having to do with an ancient Greek musical piece played either as an instrumental or to accompany the recitation of epics.