A physical act that involves running at your target, usually another person, then jumping and twisting in such a way that your ass lands as high up on their body as possible (preferrably the face). This act can be performed from a higher location, such as a bench or car, in order to get your ass as close to the target's face as possible. The only requirements to qualify as a Flying Buttress are that your feet leave the ground, and that your ass hits the target before any other part of your body. A knockdown is considered a bonus.
Everyone feared Tony's Flying Buttress' because he usually performed them without pants.
Before performing the handstand, pull down your pants just below the ass cheeks while attempting to conceal the action with your shirt. Then stand in front of a crowd, or a "target" and get in a handstand with your ass facing them, causing your shirt to fall and reveal your ass. Bonus points if you can pull off and maintain the goat during.
Did you see Jaime's Ass Handstand? It was blinding!