When in close quarters with other people, such as an elevator, you feel a huge fart coming on and you do not want to embarrass yourself, so you successfully hold it in. By the time you get off the elevator, and to much disappointment, your body has reabsorbed it, resulting in "fart failure".

Literally everyone, ever. Including the writer of this definition.

Holding in a fart to avoid embarrassment and then moving to a location more private where you no longer feel the urge.