I think the definition has narrowed over time and the new definition is not really accurate. Back in the 70s, an atheist also included those who lacked any belief in God (as also in unknowing or not knowing one way or the other without empirical evidence - babies fall into that category), not just one who denied its existence. However, nowadays many consider that to be agnostics - not just believing it is impossible to know God or of God or if God exists but also uncommitted and unknowing.

I don't know how it changed, but somehow it has.

Hmmm.....ok. That's kind of odd, because I've always viewed it as the following:

Atheists - "There is no God. Period. If others want to believe in God, fine, that's they're choice, but they're believing in fairy tales."
Agnostics - skeptics.....questions whether God exists....basically, a "I don't know"...or "we can't know for sure"

I have never believed in God a day in my life - though I've been known to quote Joseph Heller, who said he didn't care one way or another if God existed.

FWIW, I've had stronger debates with agnostics than with believers. (Kind of like when House praises Foreman for disagreeing, and rips Cameron for reluctantly agreeing) :)

Even if (total hypothetical) someone proved that God existed (which actually would wreck religion), it would have zero impact on me.

Besides...if God DID exist, he'd make a 7 inch iPad for me!!! <s>