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1.
The word ‘fannon’, generally regarded as an unstable neologism but gaining popularity as a slang term in parts of East Anglia (United Kingdom), is a noun or concept - often used in general conversation – having the literal meaning of a tear in the perineum which conjoins the vagina and the anus, giving the appearance of one orifice instead of the biologically normal two. Fannon can also be used as a technical term, when this rip occurs due to accident, operation, birth or extreme penetration.
1. "Holy shit, that girl has a fannon!"

2. "Seriously, she's so hot I could give her a fannon right NOW."

3. "Yeah, Andrew was such a large child he gave his own mother a fannon"
by Tishiam July 16, 2006
 
2.
Fannon- n. in the ancient Greek dictionary, means extreme, unusual stamina.
Fannon was considered to be an enigma due to the extreme stamina that one shows and can be very rare in normal people..
That guy lasts so long he is a fannon
by jillus77 February 07, 2010
 
3.
A fanfiction term meaning the opposite of cannon. Something totally made up by the readers/watchers.
In Harry Potter, harry and Ginny have a fannon relationship
by Mimi April 17, 2004