There are 2 definitions of flex in English:

flex1

Syllabification: flex
Pronunciation: /fleks
 
/

verb

[with object]
1Bend (a limb or joint): she saw him flex his ankle and wince
More example sentences
  • All these bones articulate with other bones and are able to make tiny interdependent movements, as well as bend or flex themselves.
  • Over the last few days I've been thinking about all the things I won't be able to do with the limb; flex my ankle, wiggle my toes, point my foot left and right.
  • As you flex your ankles, knees and hips, the angle of your front shin with the ground should match the angle of your spine with the ground.
Synonyms
1.1 [no object] (Of a limb or joint) become bent: prevent the damaged wrist from flexing
More example sentences
  • Simultaneously, he thrusts his shooting arm to full extension, his hand and fingers flexing downward at the wrist in order to impart a gentle backspin as the ball is released.
  • Her fingers flexed like the arms and legs of a ballet dancer, fingernails glossy pink, although never polished or buffed.
  • Stepping out of his dark blue 1976 convertible, David walked slowly up the driveway, steadily ignoring the way his left hand flexed in and out of a fist.
1.2Cause (a muscle) to stand out by contracting or tensing it: bodybuilders flexing their muscles
More example sentences
  • They stood before them, flexing their godly muscles.
  • But it is eerily impressive, like watching a brilliant young bodybuilder flexing his steroidal muscles.
  • Loveable cartoon character Popeye always flexes his biceps when he wants to show off his muscles.
Synonyms
tighten, tauten, tense (up), tension, contract
1.3 [no object] (Of a muscle) contract or be tensed: a muscle flexed in his jaw
More example sentences
  • End the movement with the dumbbell over your upper chest and with your pec muscles flexed as hard as possible.
  • He was still standing there when she went back into her room, his arms crossed, the thick muscles of his biceps flexing.
  • Jim's jaw muscle flexed and he continued to unwrap the shirt bits from Blair's arm.
1.4 [no object] (Of a material) be capable of warping or bending and then reverting to shape: set windows in rubber so they flex during an earthquake
More example sentences
  • Over time, as the boot leather flexes, stiffness decreases.
  • An experienced player can tell by the stick's vibration whether or not the stick flexes too much.
  • A collective puff of expelled breath flexed through the courtyard, liberated pirates rubbing their eyes to be certain the welcome, if not morbid, sight was real.
1.5 (usually as adjective flexed) Archaeology Place (a corpse) with the legs drawn up under the chin: a flexed burial
More example sentences
  • They did, however, think the skeletons looked very unusual, being very highly flexed, like Peruvian mummies.
  • Despite the length of the pit, the proximity of these articulated extremities and the ilium shows that the primary burial was in a flexed position prior to disturbance.
  • Some adults and children were subject to secondary processing after initial burial in flexed or extended positions in pits located inside the house.

noun

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The action or state of flexing: add rigidity and eliminate brake flex
More example sentences
  • This new Kenda has low, square knobs that eliminate knob flex and give positive, predictable traction on even the hardest surfaces.
  • The idea is to stabilize the scope tube and eliminate tube flex, which is still disaster for a scope.
  • The design adds tremendous strength to your whitewater stroke while retaining perfect flex.

Origin

early 16th century: from Latin flex- 'bent', from the verb flectere.

Phrases

flex one's muscles

see muscle.

Definition of flex in:

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Word of the day humoresque
Pronunciation: ˌhjuːməˈrɛsk
noun
a short, lively piece of music

There are 2 definitions of flex in English:

flex2

Line breaks: flex

Entry from British & World English dictionary

noun

British
A flexible insulated cable used for carrying electric current to an appliance.

Origin

early 20th century: abbreviation of flexible.

Definition of flex in: