Similar to a cream pie where a male ejaculates in a female's vagina, it's when a (typically larger) prison inmate rails his prison bitch in the ass and reproduces this "cream pie".
Bubba : come here pretty boy I hope you're hungry
Timmy : please no! I don't want another prison pastry!
Timmy : please no! I don't want another prison pastry!
by Johnnybertone March 27, 2014