The human mouth.
Zip up your piehole, or I'll zip it for you.
(v.) -ing, -ed, etc. To shout down opposing views on blogs, or to be excessively vigilant in routing out potential trolls. From a dailykos.com diary entitled, "Shut Your Fucking Piehole" on the counterproductivity of discussing a favored candidate's mistakes.
We encourage honest intellectual debate, and try to refrain from engaging in flaming and pieholing.