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1. Physiology Being an involuntary action or response, such as a sneeze, blink, or hiccup.
2. Produced as an automatic response or reaction: reflex opposition to change.
3. Bent, turned, or thrown back; reflected.
4. Reflexed.
a. Physiology An involuntary response to a stimulus.
b. reflexes A person's ability to respond to new or changing stimuli: His quick reflexes make him a good taxi driver.
2. Psychology An unlearned or instinctive response to a stimulus.
3. Linguistics A form or feature that reflects or represents an earlier, often reconstructed, form or feature having undergone phonetic or other change.
a. Something, such as light or heat, that is reflected.
b. An image produced by reflection.
c. A copy or reproduction.

[From Middle English reflexen, to refract light, bend back, from Latin reflexus, past participle of reflectere, to bend back; see reflect.]


Acts that occur involuntarily—such as blinking—are the result of a reflex response.
References in classic literature ?
I made notes of my patient's pulse and temperature, tested the rigidity of his muscles, and examined his reflexes.
My pulse upon examination was ten beats above the usual, and my reflexes were increased.
On the whole, the recruitment curve consisted of 45 reflexes elicited at different nine electrical stimulation intensities (5 successive recorded H-reflexes in each intensity).
Retinoblastoma is suggested by a whitening of the reflex, white spots in the reflex, an absent red reflex, or asymmetry of the two red reflexes when viewed from various angles.
Sensitivity of monosynaptic test reflexes to facilitation and inhibition as a function of the test reflex size: a study in man and the cat.
The fear paralysis reflex (FPR) may be described as one of the many primitive reflexes that all primates possess.
THE AMAZING THINGS YOUR NEW BABY CAN DO All babies have certain automatic movements they're born with - reflexes that help them protect themselves.
Spasticity is a complicated clinical symptom, characterized by a velocity-dependent increase in tonic stretch reflexes (muscle tone) with exaggerated tendon jerks, resulting from hyperexcitability of the stretch reflex [3].
Startle reflexes have evolved as fast defensive (usually escape) responses in animals, engaging subcortical reflex mechanism that bypasses cerebral processing and voluntary movement.
The effects of fatigue on balance (1, 8), maximal voluntary contraction (MVC) of the triceps surae muscles (3), and spinal reflexes (Hoffman reflex or H-reflex) (3, 6, 7) have been documented.
There are zones and reflexes on your feet and hands that "mirror" your entire body.
We report a case of West Nile poliomyelitis with preserved deep-tendon reflexes, diminished sensory nerve action potentials, and pathologic findings which do not localize to the anterior horn.