The action of leaving a social gathering under the pretence of needing to check on something urgently, but really it's because you need to poop in the comfort of your own home.
When someone poops into someone elses butt-hole, and then they poop it back into their butt-hole, with the same poop. Forever.
"Like I'll poop into her butt-hole. And then she'll poop it back... into my butt... hole. And then we'll just keep doing it back and forth. With the same poop. Forever." Poop back and forth.
When two people line their assholes up facing each other, and one poops into the others asshole, and then the other person poops right back into the first asshole, and this goes back and forth for as long as they want.
Refers to where you are unknowingly expelling a "separated pair" of stumpy poop-logs (rather than just a "standard" one-piece turd of considerable length) with a sizable "gap" of pressurized methane in between them; the result is an explosive whooshy bang partway though the dump that echoes hollowly in the toilet-bowl and is amplified/intensified by said bowl, just like the sounding-board of a drum or stringed instrument.
A backfire-poop can be highly embarrassing for the pooper if others are within earshot at the time. Some guys, however, are actually proud of making these "impressive" anal indiscretions, since it proves that they only produce "manly-sized" turds which "seal in the combustion", with no blow-by from a minuscule-diameter poop-log's allowing the gas to wastefully/splutteringly seep past the emerging turd in a much-less-spectacular noise-display.