Parabolic means symmetrical. The front and back of the skis would be identical. None of them are, only one manufacturer even came close to this. All skis have a shape. They are all narrower in the middle than at the ends.
Conventional skis are narrower at the ends than shaped skis and are considered straight skis.
A few years ago I demoed shaped skis at Whiteface. I tried an Olin Radius at 200 centimeters and a brand I will leave Nameless at 198 centimeters. I liked the Olins and disliked the Nameless. I found I could ski the Olins by just putting them on edge. This allowed me to alter the turn if I wanted to.