What's a "supernatural entity"?

The naive impression of "mind" in general philosophical discussion is a good example of a supernatural entity -- the concept of mind separated from a specific human brain, some almost spirit-like entity.

In order to commit the mind-projection fallacy, you have to forget (really: not notice) that your brain actually exists and is not an objective observer of fact, but only an opinion-generating machine. Thus, discussions of consciousness and "qualia" are hugely hampered by forgetting that the mind is not an abstraction, it's a specific physical thing, and that the various properties being attributed to it in these discussions exist only in the brain of the beholder, rather than in the thing being discussed. (As a natural consequence of physics not having layers or levels.)

The word 'supernatural' is ill-defined: if something exists in the real world, then it is natural by definition.

Exactly.