Vortex Ring State
It sounds like he was trying to explain Vortex Ring State where one can imagine it being like a vaccuum (as an explanation for the novice) and sucking you out of the sky.
As we all know, it requires (amongst other things) some downwards motion of the aircraft so technically it's not in the hovering state... but I would suggest that's the state he was trying to explain.
As far as hovering limitations are concerned, TGT or TQ time limited operations spring to mind first.
Hope this helps.