Probably, [Sam] Perkins just wanted to get out of the way and not be "posterized," which is what happens when the dunkee is humiliated by the dunker. But [Michael] Jordan thought Perkins, his college teammate, would try to block the dunk, so he switched the ball from his right to his left hand at chest level. […] Jordan extended his left hand, and flipped the ball off glass, with reverse spin, into the basket. […] Only one other such spectacular shot in a game of consequence comes to mind, the time in the 1980 NBA finals when Julius Erving wrapped himself around the basket, going out of bounds while in the air in the process, and posterized Kareem Abdul-Jabbar and Mark Landsberger with a reverse one-hand flip off the glass.
Source: wiktionary