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The hole of a volcano, which spouts out lava and smoke during an eruption.
Mount Pinatubo must have had a huge volcanus to black out the sky for so long after it erupted.

"You're from Iceland? That's just one whole island of volcanuses...you can't trust people who live on volcanoes, and I certainly wouldn't lend them money"

After eating a pizza topped with chillies, John's anus felt like a volcanus.
by professor poo April 16, 2010
A term used to describe the unbearable burning sensation of your anus during a bowel movement that usually occurs after injesting spicy, exotic, entrees
That Thai food gave me volcanus. I was late for my meeting because I had to put the flames out.

spicy butt
butt lava
burning bum
by Wildman Bill June 18, 2009
Also known as a "barnacle." This sea creature makes home to a sharp and hard surface, in which it hides in while not feeding. The reason it is called a "Volcanus" is because it resembles a Volcano and a Anus at the same time. They cling to rocks, whales, sharks, and other ocean dwellings. Known for a high bacterial content, most SCUBA divers and snorkelers wear gloves when traversing underwater reefs to protect their hands from being cut. If cut by a Volcanus, the injury will not heal completely for a few weeks, thanks to the high bacteria percentage in the creatures hard surface.

(Volkilnos the Volcanus Voyeur invented the term.)
Damnit, I stepped on a Volcanus and it cut my foot as I tried to board Volcanus Island 1.
by "Sketchy" Mike September 07, 2007
Intense diarrhoea, resembling a volcano. So intense that when fecies exits, it does so at such speed to cause a splash in the toilet water which makes contact with the buttocks.
Man, I had such a volcanus today, my ass was drenched and stinging madly afterwards.
by Blake January 17, 2004
n. An uncomfortable and often daylong affair during which one's bowels feel as though they may erupt at any time, similarly to a volcano. Often accompanied by unusually noxious flatulence including a distinct "hot" feeling. Most of the time, even a full release won't actually bring relief due to the lingering burn and difficult-to-contain aftershocks.
We had to stop a few times on our trip because of Tom's volcanus.

I don't think I can do squats today, I've got some pretty bad volcanus.
by Pcppc August 12, 2013