Lil Wayne Claps Back At Mark Cuban, 'I Will Piss In Ya F'n Mouth Ho'

Lil Wayne once said "You don't want to start Weezy, 'cause the F is for finisher" ... and he's proving to back his words with Mark Cuban -- firing back in his beef with the Dallas Mavericks owner and saying, "I will piss in ya f'n mouth ho."

The back-and-forth between the rapper and billionaire has been brewing ever since the Young Money rapper called Luka Doncic a "ho" on Twitter last week ... prompting Cuban to respond after Dallas defeated the Suns by 33 points in Game 7 on Sunday.

Wayne didn't take the jab lightly ... unleashing a pretty disgusting response to Cubes in a since-deleted tweet.

"Mark Cuban don’t make me get u smacked boy U playing w me??" Tunechi said. "I will piss in ya f'n mouth ho."

Shortly after, Wayne followed up for good measure writing, "Ya lil bitch its up."

Now, Wayne might have been a bit of bad luck for the Suns -- as soon as he tweeted about Luka, the Mavs turned the series around and ended Phoenix's season in blowout fashion.