Thank you for your apology too, but it want necessary. You were forgiven, I suppose, since I didn't take any offense.

(again semantics lol)
I see now much better what you meant. The problem I see is that antitheist does not seem to have an agreed-upon definition? I checked several places, and the definition I saw highlighted was "does not believe in God". Maybe the problem is with the sources, but as I recall I checked Wikipedia and a handful of common dictionaries.
(And by the way, if those definitions are accepted, the hyphenated word is fine as you use it.)
Maybe the terms will become more widely agreed upon and understood? I tended to mostly use the terms atheist (to mean one who does not believe in the existence of a God) and agnostic (to mean one who is not sure if there is a god, and may believe it is impossible to know). I have nor normally used the term antitheist myself, so I looked up various sources for a definition to see if I understood it correctly.
(My spell check still dies not identify antitheist as a word.)
The word I was searching for initially was for a person who believed in the EXISTENCE of God, and yet consciously chose to reject Him. (I suppose the way the demons believe in a God, yet I would guess reject Him, since they chose to rebel.) I don't have a term for someone like that.
If they were in the faith, yet chose to leave, they are apostate? (I think?) And yet, what if they simply chose to reject from the beginning?
Such a person makes no logical sense to me, unless they totally misunderstand Who God is. I can understand a person who doesn't believe God exists "rejecting" Him, though as Sarah said, it is because in their mind there is nothing to reject. That is at least logical. But to know God and reject Him, I cannot understand. Such a person may not actually exist, because they cannot have faith to believe if God does not give it to them. The question at that point would be whether they are then capable of resisting, but I guess we get into the whole free-will vs. predestination at that point, and that wasn't my intent.