When a man is receiving oral sex from a woman and is defecating at the same time(aka blumpkin). However while defecating the woman takes a hold of the fecal matter and forces it back up the anus, hence the term reverse.
In simple words, a woman is giving a blumpkin and shoves the shit back up the mansass.
Lucas: Yo Emily, Ben said that Reverse Blumpkin lowkey hurt.
When a girl is on the toilet taking a shit and leans forward to give you head
Man last night was crazy... I followed her into the bathroom and she said she had to take a dump. I wanted a reverse blumpkin “pauly” so reluctantly she gave in.
A sexual act in which someone sucks you off while they're taking a shit, resulting in them busting a nut all over the freshly laid pile of poop. Creating a glazed "poonut."
She was totally down with the reverse blumpkinglazed poonut. So we did it in the bathroom at the church her parents make her attend for all to see.
The unspoken act of a female performing an upper decker, whilst a male counterpart carries out a defecation in the lower (relative to aforementioned upper deck) deck, whilst eating out the aforementioned female.
Gary and Bruce were both really excited to partake in the sensual act of a Double Upper Decker Double Reverse Blumpkin, but neither one had eaten a large enough meal to carry out the act.