The Cleveland Browns QB was taking questions from the media at his daily press conference when he got fed up with a reporter ... and chewed the guy out in front of everyone.

ESPN Cleveland's Tony Grossi was asking Baker about a drive where it seemed the offense was moving with a "lack of urgency" and wanted to know what the deal was.

Baker started to answer the question ... but when Tony kept prodding, Mayfield lost his cool.

"I just told you the clock was running and we had a penalty! Do you wanna give them the ball back? No! You don't play, you don't know it. That's just plain and simple."

Rossi asked if Mayfield was ultimately happy with the drive ... and Baker went in AGAIN!

"Was I happy with the drive? No! We didn't score points. That's the dumbest question you could ask! What? Jesus, Tony."

Mayfield immediately ended the presser and walked off.

Afterward, Baker tweeted ... essentially saying he's NOT sorry for the exchange and this is just the kind of person he is.

"Everybody wants to hear the truth until they actually get it," Baker tweeted.

"I am who I am and always have been. Don’t call it emotional when it’s convenient and then passion when it fits. I care about winning, so yeah I’m frustrated."

"If I was to act like it’s okay to lose, then y’all would say that I’ve gotten complacent. My sense of urgency is at an all time high. And if I offend anybody along the way... that’s too bad."