(n): One who has a mastery of the anus which allows them to "cut off" a poop, before they are finished. Very effective loaf cutters are able to slice a poop many times, in such a way that the finished product appears similar to a busted roll of pennies or a sliced banana.
z: "Don't you think q would wanna come here Pearl Jam?--they're coming on the radio in a couple of seconds."
x: "Yeah, he probably would, but he's on the can now, he said he really needs to poop."
z: "Yeah but he could get out here pretty quickly, he's a Grade A loaf cutter, he could just save the rest for later."
x: "You're thinking of v, aren't you?"
z: "Nah, q."
x: "It's on!! Are we going to get him or not?"
z: "Forget it, I'm probably thinking of v..."
A loaf cutter is when someone places anothers nose in between their ass cheeks with the nose bridge centered on the butthole. When the spontaneous individual defecates, the poo will be split in half by the nose bridge, thus evenly dispersing the poo onto each side of the face.
Susan was feeling adventurous, so she decided to let Brian give her a loaf cutter.