SEX. "pie" is a word used as a cover up word for sex, for when you feel the need to talk about it and you surroundings are not suitable eg there are children in the area.
I had the best pie last night.
Also Pies are good at being devided into 5, so this give you a good way to rate sex
I had 3 slices of pie last night (average sex)
I had 5 slices or pie last night (great sex)
As you know there is also differnt varients of the "food pie" and so there is of the "sex" pie
cheery pie = sex with a vergin
apple pie = sex with an american
frog " = " " a french person
haggis " = " " " scottish "
meat " = " " someone thats 1 mixed oragin
and so on
cow pig = sex with a fatty
slim fast pie = " " " skiny person
mississippy mud pie = anal sex