A personality trait formed of boasting about sex/sexual activities usually done by a person who has recently begun having sex after a long dry spell. The change in subject to sex in the group is also likely to have been brought up by the same person, making tenuous links to otherwise non-sexual discourse.
(Flexing about sex)
(Flexing about sex)
Person 1: Jake wouldn’t stop going on about how many times he has sex last week
Person 2: yeah he’s got sex-flex at the moment
Person 2: yeah he’s got sex-flex at the moment
by Plsplsplsno July 13, 2020
Get the Sex-flexmug. 
Fully dedicating your time and effort into unlocking an acheivement in a game to the point where you haven't showered in days and then sharing for everyone to see in a sort of bragging kind of way
You seen the new gun that just came out in COD? It literally just came out yesterday and my friend unlocked everything for it already. It was all over his social media. Major sweat flex.
by AwesomeAlex808 January 26, 2020
Get the sweat flexmug. by ShortStackB January 25, 2020
Get the Flat Flexmug. The act of “putting your money where your mouth is” by rising to the occasion or backing down. Much like “nut up or shut up”, it is a challenge to someone who has said that they would do something to show strength—usually an aggressive or bold course of action. It is frequently an ultimatum to call someone’s bluff after they’ve been running off at the mouth about what they could or would do in any given situation. The term is used to shut down foolish declarations made by wanna-be types who have something to prove to themselves and others, but they often lack the ability to follow through.
Girl #1: “If Karly tries to step to me, she can catch these hands!”
Girl #2: “I think Karly might have heard what you said…she’s coming over here.”
Girl #1: “I don’t care if she heard!”
Karly: “Oh, yeah?!? Flex or fold!”
Girl #1: “JK, Karly…you know you’re my girl.”
(After mean-mugging Girl #1)
Karly: “That’s what I thought.”
Girl #2: “I think Karly might have heard what you said…she’s coming over here.”
Girl #1: “I don’t care if she heard!”
Karly: “Oh, yeah?!? Flex or fold!”
Girl #1: “JK, Karly…you know you’re my girl.”
(After mean-mugging Girl #1)
Karly: “That’s what I thought.”
by Gemini Grammarian February 4, 2022
Get the Flex or foldmug. by Protegent December 2, 2017
Get the flex valuemug. While I was presenting my project, the student across from me thinks he can start feather flexing by cutting me off and asking all these questions.
by JG.F.AV November 3, 2019
Get the feather flexingmug.