Of, relating to, or dealing with existence.
Based on experience; empirical.
Of or as conceived by existentialism or existentialists: an existential moment of choice.
Linguistics. Of or relating to a construction or part of a construction that indicates existence, as the words there is in the sentence There is a cat on the mat.
adj 1: derived from experience or the experience of existence; "the rich experiential content of the teachings of the older philosophers"- Benjamin Farrington; "formal logicians are not concerned with existential matters"- John Dewey syn: experiential 2: of or as conceived by existentialism; "an existential moment of choice" 3: relating to or dealing with existence (especially with human existence)
There is a cat on the mat.
Having to do with existence. More specifically, one way it is used is to mean having to do with state of being as opposed to truth or knowledge. An "existentialist" is more concerned with how to "be" than with what is true. A good example is Albert Camus's "The Plague", in which the character determines that we can't know the meaning of life and suffering, but we should just do what we can.
I think your problem with God is an existential one, not a theological one. You You know all you need to know, you just don't live it.