When a male either flatulates or shits out of his OWN reproductive system.
A possible after-affect of a bladder exam. During the exam the bladder is inflated with air making it possible for residual air to cause a "fart" when peeing.
Sound wise a "penis fart" can resemble a queef or the sound a hose makes when extra air escapes.
I never knew it was possible to let a penis-fart until I got a bladder exam...