[Adam the Fish]

This is hard. There is not really one definition.

There is the general 'higher power' definition which fits many religions, though "a belief in something, often..." (with what comes after 'often' interchangble) would probably be a good start to my definition.

In a way, it's one of the words (like "God") that cannot be defined further than a dictionary definition, which would not necessarily convey its whole or true meaning.