So then I decided, what if I defined "exist" simply as the idea? Namely, something could exist if we could come up with a coherent idea of it. Square triangles wouldn't exist, and the integer between 1 and 2 wouldn't exist, but pretty much everything else would "exist." Unicorns would exist, God would exist (false gods would not, being incoherent).
And that fell apart when someone remarked "well, actually, every thing does exist." And he was right, my label had to be applied to each and every thing. But then it had no meaning. If a tree existed and a toy existed and everything existed, what did my label mean?
And I was stuck.
But then someone said, "well, what are people asking when they ask "does God exist?" " (because the existence of God is where everything has to be based in)
And the answer was, "is it just a conception in your head? or does He actively do things, like create the world, save people? Is he self-consistent? Or filled with a mess of contradictions like other gods are? Is he knowable? Even if he does exist, what does that have to do with me?"
And I realized that that was the key. Trying to get someone who asks "does God exist" to define "existence" is actually quite difficult, almost a red herring. But we certainly are equipped to answer those questions posed above. And we should.