Push Pencil

Verb. The act of pooping immediately after a meal. Very much like the pencils with lead cartridges where you stick a cartridge in one end, and one comes out the other end.

Noun. One who frequently poops immediately after a meal.

“Mmm! This pot roast was delicious, but I gotta go push pencil!”

“It’s time to cut the cake! Where’s Frank?”
“Oh he’ll be out in a bit. He’s a bit of a push pencil.”