In reply to Misha:
If I have to, I tend to refer to it as something like "6b ground", with a clarification if needed regarding the length of the 6b in question. But that's more about sections of climbing. For example, I've referred to the top section of my project as "being like a couple of bolts of a short techy 7a+".
Otherwise I'd estimate a V or uk grade if it was for an individual crux. So if you were saying you had a 6a with what you're thinking of as a "6b move crux" I'd probably say "its cruxy", "probably a V2 crux". Or "don't worry, that move wouldn't look out of place on a fr6b", if they've just been shut down by it!