When one is using the public washroom and in the process of excreting, lets out a loud, resounding, fart. Followed by a loud echo in the room, it results in extreme embarrassment for whomever is present.
(Two friends using bathroom mirrors)
Friend 1: "Hey, can I borrow your lip chap?"
Friend 2: "No problem, here you go."
*Interrupted by a loud, bodily noise*
Friend 2: "Holy crap, I can't believe that just happened!"
Friend 1: "You're telling me. That was a huge Toilet-Bowl-Ringer if I've ever heard one!"