A condition in which someone feels compelled to constantly bring things that make them look good in casual conversation. It can be the same thing every time or a variety of things; as long as the subtle or obvious aim is to make themselves sound or look cool, it's a flex, and if it happens all the time, it's chronic. It's most obvious when a detail is tossed in that is really unnecessary for any other purpose than flexing.
"Man it's hot out. I haven't been in weather this warm since the day I met Barak Obama in high school."
"Still suffering from Chronic Flex, huh?"
"I'm a size medium… I haven't been able to wear a small since I started lifting."