When you let out a risky fart and a little bit of poop comes out, but the suction of your asshole pulls it back in. Just like how Prairie Dogs poke their bodies out of their hole and go back in. If you check your underwear shortly after, there might be a little shit stain.
When you know your chick has to poop so you wrap her up so tight with the sheets that she can't move her arms and then butt fuck her while she's pooping
The ack of tightening and loosening one's anal sphincter muscle to contract and retract fecal matter in and out of one's butt hole while giving yourself or receiving a traditional hand job.