There was a recent post on our local scooter group's meet-up page asking if it was "technically a maxi-scoot" club because many of the rides were pegged at 125cc or above.
I've seen several semi-definitions of maxi-scoot.
The first is used by many to refer to any scooter of 400cc or larger though these folks might include the BV 350 in that category because of its performance capabilities.
The other refers to body style, aka Burgman, Silverwing, Honda PCX, Kymco Xciting, Piaggio X and MP3 series regardless of engine size as opposed to the classic upright style of a Vespa, Sports City, Kymco People.
The third use I've seen is a combination of one and two with the more Asian foot forward body style and marked as a 400 or higher.
I tend towards the second definition based on body style though I think of the Honda PCX as a mini-maxi so perhaps that makes me use the third definition after all.
So what is your definition?