The echoing sound produced when a person lets loose a particularly loud flatus while sitting upon a toilet seat. The fart is issued, and the individual feels the vibrations as it reverberates through the porcelain, ripples the water, and the unique sound reaches his or her ears. Particularly powerful ones may even travel along plumbing lines.
Man, I hate using public restrooms. I was in a stall the other day and my neighbor let loose this explosive zeblow that I felt through the floor.