A fork of Rural Dictionary
When you have to jiggle your penis to get out that last drop of pee out.
Bryan: What took you so long to take a piss? Chris: I had to shake one out. Bryan: Oh, I hate that.
When one shits in their pants and then shakes the poop out of the bottom of their pant leg.
I was on stage and I had to shake one out and it wound up hitting someone in the front row.