When you see a girl so hot, that you cant control your man parts, and you jizz in your pants unexpectedly

to suddenly, and with no apparent reason, burst into flames and within minutes become a human cinder. a.k.a. SHC

Usually said after relaying a chain of events to make them sound more interesting.

The occassion when a human being may spontaneously burst into flame with no external interference. Generally happnes to the aged. Most victims do not survive, and combust when alone. Therefore, there are not many witnessess to spontaneous human combustion, or S.H.C.
However, there have been people who have suffered S.H.C and survived, albiet for only a short while afterwards.

S.H.C does not tend to leave much in the way of bodily remains; most victims leave just the lower leg, a singed hole in the floor, and a pile of greasy ash.
Reasons for this are still only theories, but the extreme heat required to reduce a human body to ash in the space of minutes is intense, and the flames act unaturaly.
In one such case, an elderly doctor spontaneously combusted whilst at home alone. When found, his kneecap and ashes where in the basement, and his foot and slipper left on the lip of the hole on the floor above. His aluminium walker, that should by all means be a puddle of molten metal, was fully intact, including the rubber tips.

S.H.C is not a proven phenomena, and is not a recognized cause of death.

Spontaneous Self-Combustion is a more formal way of describing the act of spontaneously self-combusting. A more graphic description of Spontaneous Self-Combustion is where a flame inside the body bursts into a flaming outbreak, consuming the body and possibly the surrounding area.
The concept of Spontaneous Self-Combustion first appeared in writing in a Charles Dickens novel. Could the idea be linked with vampirism (burning in light), love (an internal flame of love) or smoking (accidentally inhaling/swallowing lighters, and/or fuel - don't try that at home, or anywhere for that matter)?
The practicality of Spontaneous Self-Combustion is questionable; can a human (mostly made of water) really spontaneously self-combust? Not that I am trying to taint the fun, or anything.
Spontaneous Self-Combustion is a fairly surreal concept to most, so fire-proof underclothing has not yet become necessary. Not yet.

When a person, or Republican, randomly bursts into fire.

it Is a gay fighting move used during sex

To let one rip
First coined on the hit show:south park

A rapidly growing phenomena where a guitar in a public place inexplicably ignites, destroying the instrument and often severely injuring the person holding it.

Most theorists agree that it is a karmic occurrence, brought about by the disruption of peace in the universe, by a growth in the crust punk trend, specifically in the American Midwest.

Guitars tend to explode at a high enough temperature to ignite dirty clothing and greasy hair, so it is typical for the person holding to guitar to catch fire as well. Not surprisingly, there has never been an incident recorded where someone has tried to extinguish a victim of SGC, though many have admitted to thanking God after witnessing the miracle.

Researchers have been trying to establish a cause-and-effect relationship between SGC and the Mayan prediction of the 2012 apocalypse. Nostradamus' prediction has already been connected when astronomers discovered a constellation depicting SCG, perfectly situated with the predicted alignment of the planets on the day of the Rapture.

The majority of recorded cases have occurred in coffee shops, to victims who have been described as crust punk, gutter punk, and hippy.