When you're sitting in class and the need to fart overcomes your self control so the gas is expelled through the anus. when expelled you try to stop it with a quick pinch of the anus thus creating a high pitched noise (similar to that of a trumpet) only to be blamed on the asian sitting closest to you.
"Dude, I totally buttpinched in history and blamed xing xing."
by Jarcam December 13, 2008
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