agnostic, from "without knowledge," pertains to those who feel that there may be a God (or gods), but they are not convinced of it.

That's pretty much the normal definition. And, speaking of binaries, gnostic/agnostic is not a binary pairing, either, especially if you capitalize Gnostic.

If I describe myself as an agnostic it is with the intention of stating that I believe that we cannot know. This goes beyond the common definition.

More generally, I cannot agree with FF's other person if op is saying that words cannot change meaning and even diverge radically from their original meanings. One only need cite silly and nice to prove the point.