The moment where, when you're taking a shit, a large pocket of gas (referred to as a future-fart) that was resting mid-shit or between two shits escapes as you're passing your lovelog, resulting in a sudden violent fart than not only propels your previously freefalling turd at Mach 2 speeds, but also results in a pleasing shotgun blast of turdlings across the toilet bowl.
A backfire is so named for it's similarity to a car backfiring.
"Man, I was taking a dump and backfired, and now I get 'Namflashbacks when I visit the shitter."
When you are clogging the toilet with your massive, brown logs of divine terror, the brown water that splashes up on your butt and balls is known as a "backfire".
When a friend is getting head and his girl/slut decides not to swallow and said friend busts in his face (accidental/on purpose). This act is compareable to spider man shooting his webbing in his eyes.
