It was the professing atheist that decided on the exact wording. I don't like it either, but I believe he has inadvertently set himself up for failure. I believe his question sets up "reality" as the absolute standard by which all other things must be judged. So, I believe the way to "win" this debate will be to show that within a truly consistent atheistic worldview, there cannot be absolutes. If there are no absolutes, then reality is completely subjective. If reality is subjective, then all things thereunto pertaining are also subjective. Yada yada, the atheist cannot know anything because he cannot define what is really "real".
Now, of course, my opponent will borrow from the Christian worldview because I firmly believe he will not admit to the absolute absence of absolutes (thereby confessing an absolute). In doing so, he would effectively forfeit his position as "reality" would no longer be a concrete or factual thing and the conversation would be finished. He will undoubtedly make truth and knowledge claims with certainty, which cannot be possessed according to his worldview, providing me the opportunity to show him that he is suppressing the truth about the God he knows exists.