A curious term I picked up while glancing at a rant in Slashdot, "Hong Kong spin" refers to a martial arts stunt that is, in a nutshell, a backwards leap with a twist. You'll have seen it in a Jackie Chan or Jet Li film where a thug or henchman gets hit particularly hard and wants to express to the audience exactly how tremendous a blow was landed. (If the sound of bamboo sticks being smacked together wasn't quite sufficient.) Rather than simply launching themselves backwards, they'll spin around in a violent pirouette as if to indicate the direction of the blow.
With respect to the original rant, apparently such a stunt appears in the Harry Potter trailer. Nifty.