What does flex mean?
Flex is primarily a verb meaning to bend a limb or joint, most often used of tightening a muscle deliberately, as bodybuilders flex their arms to display definition. The word carries a literal anatomical sense rooted in Latin flectere, 'to bend', which also gives English flexible, reflex, and deflect. In recent decades flex has taken on a vigorous informal life as slang for showing off — displaying one's money, physique, skills, or status, often ostentatiously. From this usage comes the noun 'a flex', meaning an act of bragging, as in 'that watch is a flex'. Related compounds include 'flex time', referring to flexible working hours, and the British electrical term for a flexible power cable. Whether describing a bent elbow or a boastful Instagram post, flex conveys tension, strength, and self-display, making it equally at home in a physiology textbook and in casual conversation.
To bend a limb or joint, especially to tighten a muscle; figuratively, to display or show off something such as strength, wealth, or skill.
"The athlete flexed her knee to test the recovery of the injured ligament."
The figurative slang use is informal; the literal anatomical use is standard.
(Informal) An act of showing off; something done or possessed to impress others. Also (British): a flexible electric cable.
"Buying rounds for the whole bar was clearly a flex."
The noun sense is modern slang derived from the verb; the cable sense is chiefly British technical usage.
Applies to the informal noun sense ('acts of showing off') and to the cable sense.
"His social media feed is full of humble-brag flexes."
The slang 'weird flex but ok' became a meme precisely because 'to flex' flipped from bending a muscle to boasting about anything — even things nobody asked you to brag about.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of flex
Flex entered English in the early seventeenth century as a verb meaning to bend, derived directly from the Latin flectere, 'to bend or curve'. This Latin root also underlies a whole family of English words, including flexible, flexion, reflect, deflect, inflect, and circumflex, all sharing the idea of bending — physically, optically, grammatically, or emotionally. The slang sense of flex as showing off developed much later, emerging in American vernacular, particularly within African American and hip-hop culture in the late twentieth century, before spreading globally through internet usage.
Related word forms
How flex is actually used
As a verb, 'flex' is standard in anatomy and fitness contexts. Its figurative sense ('to flex' = to show off) is informal slang that became widespread in the 1990s and exploded with hip-hop and internet culture; the noun 'a flex' derives from it. The phrase 'flex its muscles' is common for nations or companies demonstrating power.
Easily confused with flex
Flux refers to continuous flow or change, whereas flex refers to bending a muscle or showing off.