When having unprotected anal sex, upon male ejaculation into the recipient's rectum, an anus-stretched situation may occur that results in the semen dripping out of the rectum. This is known as a dirtpipe milkshake, aka anal creampie.
Alternately, if the recipient wants to, they can squeeze out the semen on command, resulting in a dirtpipe milkshake on demand.
dirtpipe = rectum
milkshake = semen
I spl00ged up in her ass and the bitch gave my sheets a dirtpipe milkshake.
A sexual act involving anal sex in which one person ejaculates into another's rectum. That person then proceeds to pass the semen back out of their anus and then eats it.
"She just had a dirtpipe milkshake."