Rob Gronkowski BUTCHERS Freestyle Rap

Rob Gronkowski is no Eminem ... but he tried.

The NFL star ht up DJ Whoo Kid's "Whoolywood Shuffle" show with his WWE superstar pal, Mojo Rawley -- and decided to bust out a few freestyle bars over Biggie Smalls' "Hypnoitze" beat.

He rapped about Super Bowl rings. He rapped about chicks. He rapped about doorbells.

At the end, Gronk bragged that he wasn't bad for a "big ass white boy."

You be the judge.