Masturbation, jerking off, or taming your dragon at your home. Hence the "homemade" part.
Jimbo-Hey Joe wanna go to the party tonight at Silly Billy's place?
Joe- ahh..no thanks I'm gonna make some homemade pie.
Jimbo- whats that
Joe- My mom just got the magazine Good Housekeeping. So im gonna jerk off to that.
When your partner is giving you a rim job and you let something slip - They look up at you with those CRAZY-ANGRY eyes and try to yell at you but all that comes out of their mouth is shit.
Becky had to brush her teeth 5 times last night because I accidentally gave her a palin pie...
A fat pie is an overweight female, generally with some redeeming features (i.e cracking tits or nice face) who is quite tasty, although the term can be used loosely to describe any fatties.