During the inhale or exhale process of smoking a bong or other devices, a trap door occurs when the flow of air is stopped abruptly by a cough which constricts the wind pipe to the lung. This traps the smoke inside the lungs and causes extended exposure, resulting in temporary distress to the user's throat and/or lungs.
John: *sinks a bong, holds breath, then coughs all the smoke out*
Dan: LOL John just trapdoored
by fishayee June 10, 2011
The sexual maneuver, where the penis is repositioned from the vagina to the anus very quickly during intercourse.
She was getting pretty loose and bored so I pulled the trapdoor on her.

or

Connor that bastard pulled the trapdoor on me last night!
by Donald Fagen November 24, 2003
The act of disappearing during a drinking session due to too much drink/lack of money/boredom/avoidance of forfeit without letting anyone know.
They were starting on the dodgy pints and penalty gins so I trapdoored last night before it got too messy.
by UlicUK June 23, 2011
a booger, usually quite dry, that is neither in or out of your nostril. When you breathe in the out the "trapdoor" booger opens and closes.
Sheila: Damnit! I got a trapdoor and I can't seem to reach to pull it out! I need longer fingernails!
by Bubbe September 1, 2005
A sandwich so jam packed that when you take a bite everything falls out of the bottom through a massive hole that spontaneously opens up.
Dude, I made this sweet turkey club, but when i took a bite it turned out to be a trapdoor sandwich.
by Chris_Wright March 6, 2009
A booger that is trapped in one’s nose, usually stuck to the wall of the nostril, which flaps back and forth like a hinged trap door when breathing. The trap door should be removed with caution; if snorted too vigorously when trying to loosen, it may suddenly release, resulting in being sucked down into the back of your throat, Which may induce nausea or vomiting.
I’ve had a trapdoor booger stuck in my nose all day, It’s driving me crazy!
by Steve Brown (Nu) April 1, 2022
During intercourse (usually during doggy style) the man accidentally or intentionally slips his penis into the women’s asshole.
“How was your date last night?”

“Well last night was great until that bastard tried give me the Tuscan Trapdoor and I threw his ass out. So anyways I’m not constipated anymore.”
by Alibaster Slim August 4, 2012