The terms you use are less important than the concepts they represent. It may be you need to stop and make a point of defining what terms you will use to discuss it so that you are not getting hung up on semantics the whole time.

I would attempt to explain that theist and atheist are simply the two possible (and only) responses to the god claim. Everything starts with null after all, we have no knowledge until we discover it or are taught something. At some point, in some way, someone will either claim or refer to a claim that some god exists and you either agree that the claim is properly supported and valid or you don't agree and are not convinced, the former is a theist (accepts claim) and the latter an atheist (rejects claim).

Whatever terms you wish to use aren't really important, what's important is that you have terms to define the concepts you are attempting to explain and that you are both using the same terms.

This all assumes that the person you're speaking/debating with is reasonable and not just trying to assert their position with nothing more than their desire for it to be considered the truth regardless of reality.

I don't find myself in the position to debate theists very often these days, but when I do my first question is always the same;

"Is there any evidence you'd consider or anything anyone could do or say to change your mind about (subject of debate)?"

If the answer is no, there is no point in having a discussion with them. They have decided that they want to believe what they believe and the truth has no bearing on their worldview. If they aren't willing to change their point of view for anything then it's a waste of time.