“There’s a simple test to tell if one is an agnostic or not. Do you think you know for sure if any gods exist?
If so, then you’re not an agnostic.
Do you think you know for sure that gods do not or even cannot exist? If so, then you’re not an agnostic.
Everyone who can’t answer ‘yes’ to one of those questions is a person who may or may not believe in one or more gods, but since they don’t also claim to know for sure they are agnostic — an agnostic theist or an agnostic atheist.”
From: http://atheism.about.com/od/aboutagnosticism/a/Atheist-vs-Agnostic-Difference.htm
You either have knowledge of the existence (hard evidence) or you don't.
There’s a crowd of atheists who have probably been around a long time but they’re not terribly vocal whose answer to that question is “don’t care”. We’ve accepted the fact that we’re just not God worshiping people and whether or not there is one or a bunch just doesn’t matter. Maybe we need a new label, Uninterestedists or something.
The term I came across recently that I like is “Igtheist.” To the question, “Do you think you know for sure if any gods exist?” the igtheist answers, “What do you mean by “gods”? You have to be able to define something before you can argue whether it exists or not, so let’s get to a definition of “God” before we proceed.