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1.
A KFC stiffy is a great big stonking hard on brought on by the consumption of a whole bargain bucket of KFC.
"shit ive got a stonking KFC stiffy"

"i had a bargain bucket last night and my god did it give me a KFC stiffy"

"i walked into KFC last night and just the smell gave me a KFC stiffy"
by fun KFC man January 23, 2010