Angel Reese was pissed off to the max on Tuesday ... and she took her frustrations out on her coach's clipboard in the process -- swiping it out of her hands in the middle of the Chicago Sky's loss!!
The outburst happened with 29.9 seconds left in the game at George Mason University ... when Reese and the Sky were tied at 77-77 with the Washington Mystics.
As the Sky challenged a loose ball foul, players headed back to the bench ... and Reese was visibly upset.
The broadcast showed Reese going off .