"Agnostic" is used in two* different ways as well. There are those for whom agnositicism means they think it is not possible to prove or disprove the existence of any gods and there are those who just say, "Dunno." For the latter, they may think that it is possible to discover whether any gods exist, but they've not been able to do it.
People use words in many incorrect ways - when you're using technical terms in a philosophical argument, it's important to use them correctly.
OK with that, though I prefer the use of "weak" and "strong" due to possible confusion over the term "gnostic/Gnostic" and I like the idea of calling someone a "weak atheist"
I prefer gnostic and agnostic, though, primarily because - as an agnostic atheist - the 'weak' atheist argument is the stronger of the two, not that either position is inherent weak.
You don't get 'strong' and 'weak' believers, you get fundamentalists and moderates - the language we choose is important.
O.