(2) To inadvertantly reveal a piece of information that is catastrophic to your status in your social circle; to inadvertantly open oneself up to ridicule.
While receiving fellatio you shit in a pie tin. Then as you are cumming, you put the cum ontop of the poo poo. Then you shove the girl's face into the pie and force feed her the rest of the meal. This is ganranteed to be a meal she wil never forget and will talk about it for years to come.
Brian: What are you talking about?
Carina: The blumpkin pie you made me eat last night... there must have been a tainted substance in it because i feel nauseous and i think i'm going to blow chunks!
Brian: oh, well just don't get any on my shoes, they are new.
While Miles Standish was in the outhouse (after the first Thanksgiving), the hot redheaded pilgrim girl started to give him a blumpkin. John Smith came by and was so aroused that he joined in and gave her a cream pie.