That's NY Giants running back Wayne Gallman with a seriously stank allegation against Eli Manning ... claiming the QB hit him with one of the most aggressive crop-dusts of all time.

The 26-year-old RB blew the lid of Manning's putrid secret during a Q&A with NY Post columnist Steve Serby ... when he was asked to recall his favorite Eli memory during their time together in NY.

That's when Gallman dropped this [butt] nugget ...

"I wouldn’t say it was my favorite, but this is my most memorable -- we’re in the locker room before a game, he was doing his stretching while I was sitting in my chair listening to music, and he walked by and he farted by my face. And walked away."

IT WAS A HIT AND RUN!!

Serby asked, "You didn't get him back?"

To which Gallman replied, "There was no way I could get him back after that. Had to do something real nasty."

Serby again pressed ... "But, you didn’t do anything?"

Gallman -- "I didn’t get a chance to (chuckle)."

FYI, schoolyard rules state if Gallman would have yelled "doorknob" before Eli yelled "safety" ... everyone would have been allowed to punch Eli without consequence until he touched a doorknob. Everyone knows this.

Manning retired after the 2019 NFL season and has spent his time relaxing and hanging with his family.