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To run sexual tings
"dat gurl wanna run flexxes wit me"
"u wanna flex"
by Angel February 21, 2003
As far as urban slang, the definition is "to show off." Used by many rappers, most notable Ice Cube and the Geto Boys. Originated in the urban community, and has been used for quite some time.
"...no flexin', didn't even look in the nearest direction as I ran the intersection. (This is said because Ice is trying to get away from some people who tried to kill him the other day In the song, of course)" -Ice Cube, "It Was a Good Day"
by The Boston Rag February 27, 2005
dirty thingz two people do 2gether behind the scenes
ashley n mark are gonna run sum flexes
by whitepplrstupid July 05, 2005
to roll a nice L
"yoo my nigga watch me flex this blunt"
by ablazingape May 09, 2012
1) To be wearing a particular item

2) To have and item on one's person

3) To have one's hair (facial or other) cut/styled in a certain way
1) "What a legend, he's flexing dungarees"

2) "Oh, are you flexing an iPhone these days?"

3) "Dude, I can't wait till I break up with my girlfriend so I can finally flex a Hogan (moustache)"
by Guppy316 May 09, 2009
(Verb) to put up a fake front.
"Man you see all you guys are so fake, yall be flexin!"
by SirEli April 29, 2010
Anyone who thinks they are tough or tries to act tough. This may or may not be the case.
Ok Flex, quit picking fights, your 5"7" and weigh 125 lbs.
by aceface April 15, 2004
bed room parties
were having a flex at my house
by tris b March 01, 2004