The warnings given to you by your anus telling you that a shit is coming. Signs are subtle at first but eventually increase in volume and odor until you finally sit down on that toilet. Pre-Poo commonly occurs after a hard night of partying and drinking extensive amounts of beer and more often than most occurs in uncomfortable places like theme parks, business meetings, in school, and your girlfriends house. Pre-Poo, if not treated, will only get worse. Advanced stages can result in immense pain truly terrible smells.
noun - The initial rectal air blast prior to taking a shit. Most commonly used as "PPF".
(While taking shits in the locker room)
Rick: "Hey Sid, what was that menacing sound?"
Sid: "Oh it was just my Pre-Poop Fart, I ate WoW chips before practice."