flex

UK: /ˈflɛks/ US: /flɛks/ ,(fleks)

WordReference Random House Learner's Dictionary of American English © 2026

flex¹ /flɛks/   v. 

1. to bend, as a part of the body: [~ + object]
   I needed to flex my legs after the long drive.
   [no object]
   My fingers wouldn't flex.
2. Physiology to tighten (a muscle) by contraction:
   [~ + object] He flexed his biceps.

See -flex-.
-flex-, root. 

1. -flex- comes from Latin, where it has the meaning "bend.'' It is related to -flect-. This meaning is found in such words as: circumflex, flex, flexible, reflex, reflexive.

WordReference Random House Unabridged Dictionary of American English © 2026

flex¹  (fleks), v.t. 

1. to bend, as a part of the body:
   He flexed his arms to show off his muscles.
2. Physiology to tighten (a muscle) by contraction.

v.i. 

3. to bend.

n. 

4. the act of flexing.
5. [Brit.]
   • British Terms any flexible, insulated electric cord;
     an electric cord or extension cord.
   • British Terms [Slang.] an elastic band, as a garter.
6. Mathematics an inflection point.

• Latin flexus act of bending, equivalent. to flect(ere) + -tus suffix of verb, verbal action
• Latin flexus, past participle of flectere to bend, turn; (noun, nominal)
• (adjective, adjectival) 1515–25

flex²  (fleks), adj. 

1. Informal Terms flexible:
   a flex program of workers' benefits.

• shortening of flexible

Collins Concise English Dictionary © HarperCollins Publishers::

flex / flɛks/ noun

1. a flexible insulated electric cable, used esp to connect appliances to mains
   US and Canadian name: cord
2. an instance of flaunting one's attributes or possessions in an ostentatious way

verb

1. to bend or be bent: he flexed his arm, his arm flexed
2. to contract (a muscle) or (of a muscle) to contract
3. (intransitive) to work according to flexitime

Etymology: 16th Century: from Latin flexus bent, winding, from flectere to bend, bow