God would be more perfect if he could create the whole universe without even bothering to exist.
God is completely perfect.
Therefor, God doesn't exist.
QED.
If it can't handle a perfect sandwich, what hope does it have with a perfect deity?
You're right, I am conflating definitions somewhat. Arguments get squished when typed quickly into a little textarea.
My point is that people don't just mean that "supernatural" is "that which we haven't observed and thus don't understand." There is an implication that we can't understand supernatural things using theories and evidence, which is crazy. (Be careful using the word "visible" in this context. Plenty of matter isn't visible, but I doubt anyone would call electrons supernatural. I think you mean visible in the not-just-visual sense, yes?)
What does it mean to say that something exists, but has no effect on any part of the universe, no aspects that can ever be observed in any way, that leaves no footprint that can ever be detected? I think we call those kinds of things "imaginary".
When people speak of supernatural things, they do not generally mean that something is defying its own essence. What they do generally mean is that is defies what we understand to be the essence of physical matter. Our understanding of it is based on our experience thereof. So, something which is supernatural, defies classification through experiential knowledge.
We can also speak can also speak of supernatural as a sort of non-material existence, by which I don't mean Plato's forms, necessarily, but entities that exist that are not governed by the laws that visible matter is governed. Such an entity has not been widely experienced (otherwise our physics would take it into account,) and is possibly non-experienciable, so one might debate the merits of discussing it as there is clearly no reason to assume it exists. However, one cannot simply define it away.
St. Anselm in middle ages attempted to define 'God' as existing, arrived at what we now call the Ontological proof of his existence. The 'proof' was so laughable that nearly all of the Scholastics rejected it out of hand and even went out of there way to refute it. Now you seem to be presenting me with the ontological disproof. It's a little ridiculous.