1) A lesson in which you do nothing
2) A smaller version of a party in which you sit round and drink with slightly less people.
"we had a sit off because it was the end of term"
"I'm having a bit of a sit off in mine on saturday"
To sit back, relax and enjoy any free time you may have.
Our lessons cancelled... SIT OFF!
When you go into a bathroom stall to take a shit and someone else enters the restroom and sits in the stall next to you, and you are both waiting for the other to wipe their ass and leave so they can shit in private but you haven't gone yet so you fucking sit there quietly and wait for one to leave or just shit and have them listen to it. The choice is yours.
I couldn't hold my bowels any longer so I ran to the bathroom and let it explode allover the toilet, gave a big sigh and farted a bunch. I then realized my boss was in the stall next to me and I got real quiet and we had a sit-off until he got up, wiped his ass and left mumbling something under his breath, I let the rest of my shit out and shook the remaining piss out of my dick.
A lesson at school where no work is done
Wow, that religious education is a sit off. We never do anything there.
Holding up somewhere in comfort, doing very little, either with mates or waiting for something to happen
I'm so hungover, I'm just gunna go the pub to sit off with a coke.