Using your sphincter muscle to "pinch" a loaf of shit that is hanging halfway out your ass and won't drop of its own accord. Pinching a loaf always results in extra-messy wiping.
"Hurry up and finish taking a shit, we're already late! Pinch the loaf if you must!"
"Thanks for suggesting that I pinch a loaf; it worked. Now I have to spend 5 minutes wiping, then we can leave."