I've seen some BS definitions that talk about the 3rd dimension as if we are not all living in 3rd dimensional reality and thus we have to be flying in it.

My definition is:

A type of Aerobatic flying characterized by flying maneuvers that have near zero or true zero forward velocity and use proportionally "over-powered" aircraft to accomplish flying at or below the normal rated/expected stall speed.

In other words, see the big picture ads at the top of the RCUniverse page with the airplane 2 feet of the ground and 2 feet away from the pilot who is flying the plane between his house and his car and the plane is hovering in the air with the huge clouds of smoke coming out the back end.