A bowl movement that only requires one wiping of toilet paper to remove all of the poop residue from one's anus. A one wipe shit usually falls out of the anus at a high velocity and has a very solid, low liquid form; yet, it produces no splash back from the toilet bowl water.
I ate so much fiber that my poop dropped out of my anus and barely left any residue, requiring only one wipe to clean my butt hole. I wish that all of my daily shits were one wipe shits so that I could save money on toilet paper.
When you can't clean your anus after pooping no matter how many times you wipe. Usually a mechanical pencil shit is one that takes a long time to come out, so one begins to wipe prematurely before the whole poop has completely dislodged itself from the butt hole.
One's shit keeps refilling like a mechanical pencil: no matter how many times that one wipes, he can't get it clean.
This mechanical pencil shit took two rolls of toilet paper to wipe and I still haven't stopped shitting.
Mentioned by Adam Carolla on the Adam Carolla Podcast 8-11-11