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1.
The gastrointestinal distress felt as a consequence of eating at the cultural phenomenon known as Denny's. A combination of The Itis and The Shits, Shitis takes effect the instant the Denny's waitress brings your check. Early symptoms include nausea, bloating, lethargy and a sense of extreme drowsiness.

In the later stages, those affected will experience bloating, smelly gas, and explosive greasy leakage from the anus, too horrible to be considered an average case of diarrhea.

The only effective treatment for The Shitis is to build up a tolerance for food considered unsafe for human consumption. This can be accomplished by regularly consuming Fried Cheese Melts at Denny's topped with bacon, and a side of fries.
I was about to get some after taking my girl out to Denny's, but I developed The Shitis during foreplay and made a mess. At least it was in her bed and not mine.
by Dark Chocolate V2 March 18, 2013
 
2.
Pronounced "Shy-tiss"

It's a combination of having the shits and the itis. You go out, eat big meal from a questionable buffet and spend the rest of the day either crapping your pants or falling asleep, or worse, both simultaneously.
Gary: Hey Pete, you ain't looking good.

Pete: Ug, I ate at Number 1 Super Indian Buffet for lunch. Now I got the Shitis.

Gary: The what?

Pete: the Shitis. I keep falling asleep whenever I'm not pooping my brains out.

Gary: Shitty.
by J-Roc n friends November 23, 2010