A public display of useless, excessive noise usually performed by a burly biker with a beer belly showing off his loud motorcycle in a public display of faux bravado or cheesy machismo.
Bikers who are proud to frequently let their motorcycles wind out are generally insecure and they feel that letting their motorcycles peel out will compensate for an undersized penis.
There are exceptions as sometimes on occasion, even a frail, young college boy will perform a "testosterone fart" to try to impress his friends or hot girls on campus.
The burly, bearded biker showed off his loud Harley as he revved the engine through the quiet town's main drag, as he sped away when the traffic light turned green. The small town folks were not amused.
The girl remarked, "That guy needs his muffler checked!"
The boy replied, "Nah, that was just some biker dude letting loose a 'testosterone fart.'"