When the subject braces both arms (usually against the arms of a chair) and lifts ones arse in the air to create a fart with more force and power behind it.
Steve lifted his arse off the chair and let out a thunderous fart thus nearly launching himself into the air. launch pad fart arse butt
The art of defecating in a body of water, such as the ocean, a pool, a spa, etc. When Humphrey floats up, it looks like a surfacing Submarine. Sneaky tactics are often required, especially in highly populated areas.