Boxing superstar Andre Ward has a message for Conor McGregor -- STOP CALLING FLOYD A "BOY."

"I don't like that 'Boy' word," Ward told us in L.A. ... "I don't like that."

Of course, Floyd Mayweather and his father have said they weren't offended when Conor said, "Dance for me, boy" in both media events this week. 

But it ain't flyin' with Ward -- who tells TMZ Sports there would be a different response if anyone hurled that word at him. 

We also asked S.O.G. about whether he'd cross over and fight a UFC star like Conor ... and his answer will get you pumped.