A complicated art, when performed correctly 'shissing' exemplifies multi-tasking and unequivocable prowess to the hilt of mankind's uppermost eschalons. Quite literally, 'to shiss' is to excrete simultaneously, which is too say 'pissing whilst shitting...shissing'.

A fundamental quality of military leaders and comedic performers alike, shissing nevertheless assumes the position of social taboo, and is thus confined to confidential conversation and, inevitably, urbandictionary.com
Person 1: Buddy, i have an issue...i need to do a twosie and onesie...at the same time
Person 2: Don't worry, just take a shiss
Person 1: Fo' shissle
by BG.1717 June 28, 2009
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That moment when you need to take a shit and a piss at the same time.
Hold that thought, man! I gotta take a shiss!
by Mu5Hr00m November 9, 2015
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When your in a hurry(whether it be to get back to video games, dinner, or bed) and you push to hard while peeing, coincidentally shitting your pants.
I heard David in the bathroom at lunch. He was pushing so hard peeing I thought he was going to shiss!
by David smallwood February 4, 2015
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1) Dude! Pull over! I gotta take a Shiss!

2) God damn it! I think Gary just shissed himself!
by The shissmaster October 20, 2009
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A combination of shiting and pissing, you’d say it when something is really funny
Bro i’m shissing so hard
by yourmomscousin April 25, 2020
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When you are walking your dog and he attempts to lift his leg to take a piss, then re-thinks he has to shit. Resulting in a dog shitting with his one leg up. Very comical!
Good Ol' Taz took a shiss on that rock out of piss/shit confusion.
by Tiptop77 November 25, 2012
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When ones person needs to take a shit but also a piss
Man I had a good shiss last night
by Thepansexualunicorn July 20, 2017
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