situp

to leave the place that you've sat on

The action of lying down and situp to make your stomach muscles tougher

when one bounds another across the head with a shirt and tells him to attempt to do a situp while an acomplice drops his pants and points his ass at the person doing the situp, at which time the shirt is released and the one attempting his the ass with his face

This is when you get some beefcake who thinks hes hot shit to show off. Tell him that you are going to put a towel over his head and see if he can do the situp while you pull down. Being the arrogant moron that he is, he gladly tries. Have someone pull their pants down over his head and release the towel. The unsuspecting douchebag's nose goes right up the guys ass.

person 1 is baited into performing "the hardest situp ever". Person 1 then lies on the floor on their back and told cross hands on chest. Person 2 then holds a towel over the face of person 1 covering the eyes telling him sit up quickly with all his strength when he say to. Meanwhile person 3 has removed their pants and is squating over person 1's face with out him knowing. Person 2 then tells person 1 to sit up quickly and removes the towel as soon as the sit up begins. The result is person 1's nose is planted into person 2's ass.

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.

when one is conned into attempting a "most difficult" situp resulting in a firm thrusting of the suckers nose directly up the shit pipe of a prankster. Usually results in prompt ass kicking and residual smell of butt mud for several days.

The act of a person falling asleep at a party and one of his friends pulls down his pants and squats over the sleepers face, while another person punches the sleeper in the stomach, resulting in the sleeper violently sitting up and getting a face full of taint. Bonus points if the squater farts.