There have been rumblings for weeks that the All-Pro tight end was considering a comeback after retiring last season ... with the 30-year-old himself even teasing he'd be back in Week 14.

But, Gronk has finally put the speculation to rest on WEEI's "The Greg Hill Show" on Tuesday ... when one caller asked to give a definitive "yes" or "no" to whether there was a chance he could throw on the #87 jersey again.

"When I retired, I retired for a reason: because I needed to step away," Gronk said. "So, it would be a 'no.' There it is."

"I never say 'no,' because I've said 'no,' and everyone's like, 'Yeah ... he's kidding. He's coming back,' ... But it's a 'no.' In my mind, that's how it is. It's a no."

Of course, Gronk has moved on to promoting CBD Medic and has explained how it has kept his body finally pain-free after years of wear and tear.

He's also said he's had probably 20 concussions and 5 blackouts throughout his football career, so it shouldn't come as a surprise he's ready to put that behind.