The process in which bits of watery poo sprays from the anus, during the farting process.
It is also used to describe the flapping of the butt cheeks in this process.

Flatching is often seen as embarasing and shameful, it is curtious to apologise to public and people around when you have just flatched.
"I'm sorry is that my flatch your covered in?'
"I'm terrible sorry, but I flatched all over your mother."
"I dont usually flatch like this."
"Did that hurt? My flatch wasn't perticularly watery today, I do apologise."
by Java Knees November 7, 2008
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Help me get this flatch off the walls before my wife gets home!
by Sklooby March 18, 2008
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kind of like felching except you suck so hard your face turns blue
I was flatching ray's asshole last night and i burst a blood vessel.
by pierre jay February 10, 2009
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Short for "Flatuence"
"Did you just flatch?"
by Doc Evil July 24, 2003
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Flatmate, a British alternative to 'Roomie'. A more accurate term, since neither we, nor these so-called 'Roomies' actually share a bedroom. From 'Flatchum' or 'Flat Chum'.
by Flatch # 1 June 8, 2006
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Knickname for Flatulina Boutier aka: The Fabulous One
So I went up to Flatulina and said, "Hey, Flatch, can I borrow your pet monkey?" and she said, "No problem, Tootie!"
by Tootie September 13, 2003
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