A Human Flamethrower is where a take a large syringe and fill it with alcohol. You then stick the syringe down the tip of your penis and inject the fluid in. After injecting you hold a lighter at the tip of the penis and piss out the alcohol causing a Human Flamethrower.
Damn, grandma you didn’t tell me that pops did a Human Flamethrower back in Vietnam.
You fill a man's asshole with a tank of propane until the stomach expands. You then prepare a lighter at the asshole and push on the man's stomach causing a massive explosive stream of shit and fire.
Timmy thought it was a good idea to melt the ice on a lake with a human flamethrower.