Oh, you cannot be serious. You're agnostic about god, because god can't be defined? But it's not about evidence, it's about philosophy? Seriously?
The impossibility of defining "god" is a good reason to be agnostic? It's impossible to define "asdjfop". It's impossible to define because I just made up the word, and it has no meaning. I could pretend it had meaning, but I could then pretend that it was impossible to define its meaning. You must, therefore, be agnostic about "asdjfop" as you cannot define it.
It's not about evidence of "asdjfop", after all. It's about philosophy - specifically, the logical impossibility of knowing everything about existence.