1. slang A fall on one's buttocks, especially as an element of a comedy routine. "Prat" is a slang term for the buttocks. It's striving to be like the vaudeville acts of yesteryear, so expect plenty of corny jokes, pies in faces, and pratfalls from beginning to end.

2. slang By extension, any error, mistake, failure, etc., especially one that is humiliating in some way. Despite the many pratfalls in her election campaign, she still managed to pull ahead at the last moment and secure a victory. This is just the latest in a series of pratfalls that have served to undermine the company's credibility.