When your jeans are so tight, it makes it look like you are making your ass flex. Most commonly happens when you are wearing skinny jeans.
Person 1: Oops I dropped something.
(Bends over to pick it up.)
Person 2: Nasty! What are you trying to do an assflex?
Person 1: No!
by googoogoodolls January 06, 2011
Top Definition
Someone that is an uptight douchebag who lifts a lot of weights and thinks they are tough shit.
That guy just bumped into 60 year old lady cause she was in his way, what an Ass Flex!
by Slobo March 03, 2008
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