To shit someone up is to scare the shit out of them.
To be shit up is the state of being scared shitless.
"don't be shitting me up"
"lets go and shit em up"
"we shit em right up"
"they were shit up, so they shit out"
A common prank resulting in the victim attempting a blind-folded situp and encountering the perpetrator's ass at the apex of the situp.
Bart wanted to impress his friends with his ability to achieve at least one situp while resisting the force of a towel pinning his head to the ground by a buddy. Before he knew it, his nose was cheek deep in ass and he realized he had actually performed a shitup.
British prison officer's slang for an inmate seeking attention by smearing his cell with excrement.
Wow did you see that shit-up in Block 9 this morning? I pity the cleaners.
Working out vigorously with full bowels, then trying too hard to get that 'last' sit-up. At least your whole anus didn't pop out, like has happened to some unfortunate weight lifters.
Weight lifter: *pant* *pant* uuHHUNNGHHT! *sploosh*
Random hot girl walking by: Aww gross... did you just shit-up?
To do 25 sit ups after you take a shit
I just got done taking a shit, I better do my shit ups.
when a huge dump comes flying out your dunghole so fast that you are lifted off of the toilet seat
Guy: Oh shit here it comes!
'turd shoots out like a bottle rocket'
'guy's head gets stuck in ceiling'
Guy: Damn i hate doing those shit-ups.