ALISTAIR OVEREEM Suffers Gruesome TKO ... LIP BUSTED RIGHT OFF

Alistair Overeem is cracking jokes about it Sunday, but he couldn't even crack a smile after a sudden and bloody ending...

to his UFC fight, where his lip was nearly knocked clean off.

Overeem went down late in the 5th and final round of his UFC on ESPN 7 heavyweight match with Jairzinho Rozenstruik -- he was winning handily, really ... until then.

You gotta see the video of the shot Jairzinho uncorked right to Alistair's upper lip -- it's almost like his face exploded.

He managed to get back up, and attempt to grin, but the referee called the fight with just a few seconds left in the round. The attempted grin didn't work either, due to the horrific damage to Overeem's face.

A few hours later, Overeem joked on Twitter about his lip not looking too sexy.

Source: TMZ