The thing is though, we're not missing a word. Arlee, myself, and everyone over at HtP and Shadowpriest.com use "Best in SLOT" exactly as it is. OP on the other hand is using a potential "Best gear set", which is different and should be treated differently.
A person can't just dismiss what a BiS list is, because it doesn't fit what their idea of the definition should be. They're different terms altogether.