Novak Djokovic lost his cool on the court in a BIG way Tuesday ... going off on an umpire in an epic meltdown -- and the entire tantrum was captured on video.
It all went down at the Italian Open in Rome, when Djokovic got upset with an umpire for letting his match with Taylor Fritz go on despite heavy rain.
In video from the court, Djokovic can be heard exploding on the ump ... "How much more do you want to play?!"
Novak was fuming over the clay court's conditions under the falling rain .