a 'pnuematic turd' occurs when one farts in such a way as to trap the gaseous noxious mix inside one's rectum, thus creating an air pocket in one's rectum, mimicing the feeling of turding one's self.
"Oh man, I thought I just crapped my pants, but I only had a pneumatic turd. Thank God, because I do not have a change of underroos with me."
by bubbakeg99 December 28, 2010