How do you define God?

How do you guys define God? Is there any expectations for any certain characteristics? Is it a person? Or is it a sentient entity? Is it a substance?

This is not a question to try and prove/disprove God. I just want to understand what image or idea does the concept of God invoke for agnostics and atheists.

Again, I'm not looking for proving or disproving the idea. I'm just trying to grasp your conception of God.

Please mention the religion if a specific religion/s is responsible for this idea.