I define it as a gap of frames your opponent cannot beat you out on with any options, thus they are trapped by the frames. They are allowed to recover from stun, but have no offensive measure that can be taken with consideration to frames solely (so it ignores evasion properties such as invincibility, crouching, etc...). So the Amy scenario works in matchups where a character does not have an i11 or i12, but not in matchups where they do have an option. I'll clear that up though as it's misleading and usually is a scenario where you have advantage.
I'm taking notes and I'll do a proper rewrite later (hopefully i get internet back on at home today)