The NY Knicks have determined an idiot fan SPIT on Atlanta Hawks superstar Trae Young during Wednesday night's game at MSG ... and now the mouthy fan has been banned indefinitely.
It all went down with around 8 minutes left in the 4th quarter of the Knicks vs. Hawks playoff game ... when Young was trying to inbound.
Video footage shows someone sitting behind 50 Cent appear to spit at Young -- leading Young to comment after the game, "Damn ... crazy!"
Young also asked 50 Cent if he was "good" following the incident.