When you have to piss so bad, that when you finally go to take a piss and you think you're done pissing, your second bladder kicks in and you piss some more. Like a continuation of your first piss after a brief slowdown or stopage, and it starts up again.
"Man, I drank so much beer that I pissed for 5 minutes straight because my second bladder kicked in."
by Johnny Five Alive November 16, 2011