look up any word, like cleveland steamer:
 
6.
Action. To straddle someone's face and to place your asshole over that person's nose while they sleep, then as they awake from a punch in the groin...well you get the picture. Ta-da! An impossible sit up.
Matt gave Craig and IMPOSSIBLE SIT-UP and he farted in his nose!
by Godsbest September 02, 2003
 
1.
the impossible sit-up(often called the olympic sit-up) is completed by asking an individual to lie on the ground in standard, bent-knee sit-up position while one accomplice blind folds or holds a towel or similar item over the eyes and holds the individual's head to the ground. the second accomplice gets into a squatting position with ass bare. the victim is signalled to attempt to sit-up against the pressure applied by the towel to the head. the towel holder simply releases the towel which allows the victim to sit up with nose directly into accomplice two's ass crack. a fart may be added as a bonus. the name "impossible" is intended to entice an overconfident victim into attempting this athletic feat. occasionally, idiotic victims might not even require the blind fold and will simply close their eyes. technique may be modified depending on intelligence level or sobriety of victim.
"Damn Bruce, your abs are ripped! I bet you could be the first guy I've ever heard of that can do an impossible sit-up."
by monkey12 June 11, 2005
 
2.
when the sitter upper is blindfolded and then held down while he trys to do a situp. in the mean time another person puts theyre bare ass in his face and he is let go so is face smashes into the ass.
Dude we gave travis the impossible situp today and he smashed his face into codys ass, GNARRRRRR!!!
by Q ha May 16, 2006
 
3.
A dirty trick you pull on a friend at a party, where you hold a towel over a friends face while he tries to do a sit up with you pulling down on it. While your friend tries to do this sit up you have another friend bend down over him and pull down his pants then you release the towel and your friends face goes into an asshole.
Kean: Aw man I was so drunk last night but I sobered up really fast when Darren and Matt got me to do an Impossible Sit Up.
by Matt Walters April 23, 2008
 
4.
When someone (a male) is passed out on their back, you take off your pants and stand with one leg on either side of their torso, with your bare ass in the direction of their face. You then punch them in the groin with a degree of force, and they will sit up abruptly, getting a face full of your bare ass.
Fuck, Josh made me do an impossible situp last night and I swear, I can still taste his ass.
by Cacophonous Mischief January 14, 2010
 
5.
When you initiate rookies by restraining them from sitting up with a pillow or rag etc and removing it while someone stratles above the pillow with their pants down. Move the pillow and as a result the rookies face will procede into the guys asshole. Resulting in a brown nose.
Barney Dawg was so retarted he tried an impossible sit up and got shit stained . What a douche. Mccoy Sports 4 life
by COdy aka big dagg September 20, 2004