To me, God is an embodiment construct of all there is. Literally. I personally believe the brain to be a receiver of consciousness, Everything we know of is all subjective in a way. Everything we know to be true is within our own experience. The knowledge taught and read by others, the knowledge of the universe, all within our individual experience. Turn that off for everything, and what can there possibly be? Just waves of atoms and energy, there isn't any science to label physical clusters of atoms, these are all things we've learned and created through our conscious experience of the universe using our 5 physical senses. If there isn't any consciousness in the universe at all, then there is no way anything can be experienced or perceived and there is no way to perceive these clusters of energy as matter, therefor there is no reality to be created.
The idea that each of us has an entire universe within each of us through consciousness, and believing that we are all part of a greater collective, the conscious universe is what I try to describe.
I think this is the general fundamental of all spiritual and religious beliefs come from. This collective consciousness that brings all into existence, this would be "God", in my views, it's the conscious universe, or "god", in someone else's it's singularity. Everything is subjective. Our lives are subjective, period.