Pan Flash 

Letting rip a properly brewed grunt into the bowl (pan) of a toilet, then setting it alight, causing the grunt to ignite.

This is a dangerous sport, since one has to be virtually seated on the toilet when being lit, to stop a) the gasses from escaping due to diffusion, and b) the movement of getting off the bog blowing the gasses away.

This mostly results in gooch hair removal.

Shit! that pan flash nearly took my fucking gooch hair off!

Pan Flash by Steddaz October 20, 2006

Flash Pan 

Building a system of pulleys and winches with a rope and noose attached. Then, waiting for your girlfriend/boyfriend to walk through the door, ambush, and smack them over the head with a frying pan. Then, putting the pulley and winch arrangement into effect, hanging your partner up as they start to awaken from the blow to the head. While they are hanging by their neck, you get an erection and when they are just about to die as a result of asphyxiation, quickly drop them and bum them.

"Yeah, my bird came home from work last night and I flash panned her in the living room"

"Fuck off mate, I'll flash pan ya!"

"Oh your gonna get pan flashed"

"Tonight, we get Delboy off his tits and flash pan him"

Flash Pan by Matthew Booth December 24, 2008

FLASH IN THE PAN 

1. A Project, person etc that enjoys only short lived success.
2. Something which disappoints by failing to deliver anything of value, despite a showy beginning
Origin
This originally had a literal meaning, i.e. a real flash in a real pan. Muskets used to have small pans to hold the gunpowder charge. An attempt to fire the musket in which the gunpowder flared up without firing a bullet would be called a 'flash in the pan'.
origin, The term is known since the late 17th century. Elkanah Settle, in Reflections on several of Mr. Dryden's plays 1687, had this to say:

"although the group had a number one hit, it was only a one hit wonder making them a flash in the pan."

"If Cannons were so well bred in his Metaphor as only to flash in the Pan, I dare lay an even wager that Mr. Dryden durst venture to Sea."

FLASH IN THE PAN by johnny english2 January 23, 2007