This is a skill point.
You can only do this after placing 1st in the race at least once, because tricks are blocked out until you do so. In the hoverboard race at Blackwater City, take a boost and hit a ramp. In the air, hold the left analogue stick to the left and hit , , , and in any order to do a Twisty McMarx. You must make sure you do all four moves needed in the trick, and if done properly a skill point will have been obtained and the trophy will unlock shortly after doing it too.
TechStep has provided a handy alternate method for this trophy:
Seems silly but a lot of people talk about how easy this was, but sadly it took me a bit take it out. Instead of holding the stick left, hold the D-Pad "UP" and hit the buttons in any sequence. You will flip forward instead of left... i found myself flying off the track holding left too many times getting it down correct.