The retired and undefeated boxing great is obviously biting at the UFC lightweight champion's challenges to fight.
In the latest piece of smack talk, Mayweather posted an Instagram video of McGregor taking blows to the face and tapping out in the ring.
It's followed by a photo of the boxer laughing. He's offering $10,000 to the person who can come up with the best caption. He wrote,
CAPTION THIS! Best caption wins $10,000.00. The winner will be announced on Monday, Dec 19. Stay tuned ! #TMT
The video's already been viewed more than 2 million times.
It's unclear if Mayweather is being serious about the offer, but that hasn't stopped fans from giving it their best shot.
Pretending to quote McGregor, one person wrote,
I would like to apologize to absolutely fucking no one because I put this upon myself #50-0.
It's a swipe at McGregor's celebratory speech after he won against Eddie Alvarez to become the UFC's first simultaneous champion in two divisions.
Another fan trolled the fighter with a reference to the movie "Happy Gilmore." He wrote,
Come on you can do it! Just tappp it in nice and easy tapppp it in.
McGregor has publicly said he would fight Mayweather for $100 million in cash. But he said Mayweather would have to prepare for a "fight," not a "boxing match."
Earlier this week, Mayweather appeared in a live Instagram video in which he threatened to "slap" McGregor.
In the sweary rant, he said,
Imma fuck McGregor up too. Punk ass McGregor. Imma slap McGregor — imma slap the shit out of McGregor when I see him.
It would be a fantasy fight to end all fantasy fights, and I'd pay good money to see it. The reality of it happening, however, is pretty non-existent.