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

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

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

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

It can take several months for investors to fully overcome this reflex, during which traders can profit by not underreacting.

From Barron's • Mar. 24, 2026

The bots possess an exhausting reflex to present both sides of every issue, creating a false, artificial balance even when the counterargument is absurd.

From The Wall Street Journal • Mar. 5, 2026

This time, gold showed both its reflex and its restraint.

From MarketWatch • Mar. 2, 2026

It becomes activated as the baby stretches these tissues, triggering a neural reflex that boosts uterine contractions.

From Science Daily • Jan. 13, 2026

She almost sang it, her reflex to sing conjure spells ever present.

From "The Marvellers" by Dhonielle Clayton