Just to add another level of confusion: while by the above definitions I'm an agnostic atheist, in that I wouldn't claim to know for a fact that no gods of any kind exist, I tend to self-identify as someone who believes no gods exist because until some kind of evidence for gods shows up, there's no real point in wallowing in uncertainty.
The problem is, the definition of "gnostic" has no real application because claiming knowledge really means nothing if you cannot demonstrate you actually have knowledge. There is a difference between belief and knowledge, knowledge requires some rational basis and theists cannot demonstrate they actually have any real knowledge of gods. Therefore, this definition is pointless because *EVERYONE* has to be agnostic.
A better definition is based on the availability of knowledge. Do you think it is possible to have knowledge of gods? If yes, you are gnostic, if no, you are agnostic. An agnostic atheist in that setting would be someone who doesn't believe in gods, yet doesn't think it's ever possible to know for sure. I, however, would fall into the gnostic atheist camp, I don't believe, but I would have to have knowledge that gods were actually real in order to believe in them. I think it's possible to know, we just don't currently.
It's unfortunate that everyone is working from their own personal dictionary on some of these terms, then expecting the world to fall into line behind them.