reflex

American  

[ree-fleks, ri-fleks] / ˈri flɛks, rɪˈflɛks /

adjective

1. Physiology. noting or pertaining to an involuntary response to a stimulus, the nerve impulse from a receptor being transmitted inward to a nerve center that in turn transmits it outward to an effector.

2. occurring in reaction; responsive.

3. cast back; reflected, as light, color, etc.

4. bent or turned back.

5. designating a radio apparatus in which the same circuit or part performs two functions.

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noun

• reflexes
  plural

1. Physiology.

   1. Also called reflex act.  movement caused by a reflex response.

   2. Also called reflex action.  the entire physiological process activating such movement.

2. any automatic, unthinking, often habitual behavior or response.

3. the reflection or image of an object, as exhibited by a mirror or the like.

4. a reproduction, as if in a mirror.

5. a copy; adaptation.

6. reflected light, color, etc.

7. Historical Linguistics. an element in a language, as a sound, that has developed from a corresponding element in an earlier form of the language.

   The (ō) in “stone” is a reflex of Old English ā.

8. a reflex radio receiver.

9. a reflex camera.

verb (used with object)

1. to subject to a reflex process.

2. to bend, turn, or fold back.

3. to arrange in a reflex system.

reflex British  

noun

1. 1. an immediate involuntary response, esp one that is innate, such as coughing or removal of the hand from a hot surface, evoked by a given stimulus

   2. ( as modifier ) See also reflex arc

      a reflex action

2. 1. a mechanical response to a particular situation, involving no conscious decision

   2. ( as modifier )

      a reflex response

3. a reflection; an image produced by or as if by reflection

4. a speech element derived from a corresponding form in an earlier state of the language

   "sorrow" is a reflex of Middle English "sorwe"

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adjective

1. maths (of an angle) between 180° and 360°

2. (prenominal) turned, reflected, or bent backwards

verb

1. (tr) to bend, turn, or reflect backwards

reflex Scientific  

/ rē′flĕks′ /

1. An involuntary physiological response to a stimulus, as the withdrawal of a body part from burning heat.

2. An unlearned or instinctive response to a stimulus.

3. Also called unconditioned response

4. See more at classical conditioning

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reflex Cultural  

1. An action or movement not controlled by conscious thought. A reflex may be anything from a hiccup to the involuntary response of a body part, such as the action that occurs in the knee-jerk reflex.

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Other Word Forms

Derived Forms

• multireflex
  noun
• reflexibility
  noun
• reflexness
  noun
• semireflex
  noun
• reflexible
  adjective
• reflexly
  adverb

Inflected Forms

Nouns

• reflexes
  plural

Etymology

Origin of reflex

1500–10; < Latin reflexus bent back, past participle of reflectere to reflect

Explanation

A reflex is an action your body does without your thinking about it, like sneezing, or jumping a little when you dream you’re falling. If you suddenly catch a ball before it crashes into a window, you have quick reflexes. When a doctor hits your knee with a little hammer during a physical, it makes your leg kick, even though you didn't consciously make your leg move. The doctor is testing your reflexes — movements that happen without your control. If your reflexes aren't working, it could mean there's something wrong with your body. Putting your hands out when you fall is a reflex. So is laughing so hard you snort.

Example Sentences

See Examples For:

reflex reflexes

Unlike bees or wasps, which sting as a defence mechanism to protect themselves, a jellyfish sting is an automatic reflex, not a deliberate attack.

From BBC ● Jul. 28, 2026

A sensible reflex, but it also means the long-awaited payoff never quite materializes—an underwhelming finish to an otherwise engaging and illuminating argument.

From The Wall Street Journal ● Jul. 24, 2026

Even high-profile cases involving figures like Sean Combs reflect the same cultural reflex: disbelief, deflection, delay.

From Slate ● Apr. 25, 2026

Like a teenage reflex, I sprinted to the comments to see what people were saying.

From Salon ● Apr. 12, 2026

Adam touched her wrist with his finger, and her fingers moved a little in reflex.

From "East of Eden" by John Steinbeck

"We face a world situation that has changed and the institutions and practices and the reflexes that were honed and very successful in the past no longer are," he said.

From BBC ● Feb. 8, 2026

Although there may be no meaning behind those reflexes in patients with severe brain injuries, the presence of those seemingly human expressions may make it even more difficult to let someone go.

From Slate ● Dec. 8, 2025

Mr. Rein implores us to override the divisive reflexes evolution has bequeathed us.

From The Wall Street Journal ● Oct. 13, 2025

Edmunds noted the new Model Y lacks sporty reflexes but offers a comfortable ride, while the Model 3 maintains strong performance.

From Barron's ● Oct. 10, 2025

I stared; something seemed to have gone wrong, my reflexes were jammed.

From "Invisible Man" by Ralph Ellison