[adjective, noun ree-fleks; verb ri-fleks]



verb (used with object)

Origin of reflex

1500–10; < Latin reflexus bent back, past participle of reflectere to reflect
Related formsre·flex·ly, adverbre·flex·ness, nounmul·ti·re·flex, nounsem·i·re·flex, noun Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

British Dictionary definitions for reflex-act


noun (ˈriːflɛks)

  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)a reflex action See also reflex arc
  1. a mechanical response to a particular situation, involving no conscious decision
  2. (as modifier)a reflex response
a reflection; an image produced by or as if by reflection
a speech element derived from a corresponding form in an earlier state of the language"sorrow" is a reflex of Middle English "sorwe"

adjective (ˈriːflɛks)

maths (of an angle) between 180° and 360°
(prenominal) turned, reflected, or bent backwards

verb (rɪˈflɛks)

(tr) to bend, turn, or reflect backwards
Derived Formsreflexible, adjectivereflexibility, noun

Word Origin for reflex

C16: from Latin reflexus bent back, from reflectere to reflect
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for reflex-act



c.1500, "reflection of light," from verb reflex meaning "refract, deflect" (late 14c.), from Late Latin reflexus "a bending back," noun use of past participle of reflectere (see reflection). Meaning "involuntary nerve stimulation" first recorded 1877, from reflex action (1833).

Online Etymology Dictionary, © 2010 Douglas Harper

reflex-act in Medicine




An involuntary physiological response to a stimulus.
An unlearned or instinctive response to a stimulus.
Something, such as light or heat, that is reflected.


Being an involuntary action or response, such as a sneeze, blink, or hiccup.
Bent, turned, or thrown back; reflected.


To cause to undergo a reflex process.
To reflect.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

reflex-act in Science



An involuntary physiological response to a stimulus, as the withdrawal of a body part from burning heat.
An unlearned or instinctive response to a stimulus. Also called unconditioned response See more at classical conditioning.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

reflex-act in Culture


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.

The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.