re·flex ˈrē-ˌfleks 
1
a
archaic : reflected heat, light, or color
b
: a mirrored image
c
: a copy exact in essential or peculiar features
2
a
: an automatic and often inborn response to a stimulus that typically involves a nerve impulse passing inward from a receptor to the spinal cord and then passing outward from the spinal cord to an effector (such as a muscle or gland) without reaching the level of consciousness and often without passing to the brain
the knee-jerk reflex
b
: the process that culminates in a reflex and comprises reception, transmission, and reaction
called also reflex action
c
reflexes plural : the power of acting or responding with adequate speed
d
: a way of thinking or behaving
3
: a linguistic element (such as a word or sound) or system (such as writing) that is derived from a prior and especially an older element or system
boat is the reflex of Old English bāt
1
: directed back on the mind or its operations : introspective
2
: reflexed
3
: produced or carried out in reaction, resistance, or return
4
of an angle : being between 180° and 360°
5
: of, relating to, or produced by a reflex without intervention of consciousness
reflexly adverb
Examples of reflex in a Sentence
Noun reflexes such as swallowing and blinking Disagreeing with my suggestions has become almost a reflex for him. an athlete with great reflexes My reflexes are slower now that I'm older.
Recent Examples on the Web
Health, 13 Apr. 2026 When attuned and invested adults can help the frightened child feel safe, understood, and valued, these protective reflexes and panic responses are brief. —Dr. Andrew Garner, Boston Herald, 12 Apr. 2026
Liz Koch, STAT, 6 Apr. 2026 The ten seconds that led to the Braylon Mullins’ miracle shot were a series of reflex plays, reactions, the ultimate in instincts taking over, living in the split second, rather than in the moment. —Dom Amore, Hartford Courant, 30 Mar. 2026 See All Example Sentences for reflex
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
Noun
Feeding Difficulties Because of their low muscle tone, many babies with PWS have a weak sucking reflex. —Health, 13 Apr. 2026 When attuned and invested adults can help the frightened child feel safe, understood, and valued, these protective reflexes and panic responses are brief. —Dr. Andrew Garner, Boston Herald, 12 Apr. 2026
Adjective
That reflex delays care and erodes trust. —Liz Koch, STAT, 6 Apr. 2026 The ten seconds that led to the Braylon Mullins’ miracle shot were a series of reflex plays, reactions, the ultimate in instincts taking over, living in the split second, rather than in the moment. —Dom Amore, Hartford Courant, 30 Mar. 2026 See All Example Sentences for reflex
Cite this Entry
“Reflex.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.grautoblog.com/dictionary/reflex. Accessed 27 Apr. 2026.
Copy CitationKids Definition
reflex
1 of 2 noun
re·flex ˈrē-ˌfleks
1
: an automatic response to a stimulus in which a nerve message passes from a sense organ to the spinal cord and then to a point of action (as a muscle or gland) often without first passing to the brain
the knee-jerk reflex
compare habit sense 3
2
plural : the power of acting or responding with enough speed
an athlete with great reflexes
reflex
2 of 2 adjective
1
: produced in reaction, resistance, or return
2
: of, relating to, or produced by a reflex of the nervous system
reflex action
reflexly adverb
Medical Definition
reflex
1 of 2 noun
re·flex ˈrē-ˌfleks
1
a
: reflected heat, light, or color
b
: a mirrored image
2
a
: an automatic and often inborn response to a stimulus that involves a nerve impulse passing inward from a receptor to the spinal cord and thence outward to an effector (as a muscle or gland) without reaching the level of consciousness and often without passing to the brain
the knee-jerk reflex
b
: the process that culminates in a reflex and comprises reception, transmission, and reaction
c
reflexes plural : the power of acting or responding with adequate speed
reflex
2 of 2 adjective
1
: bent, turned, or directed back : reflected
2
: of, relating to, or produced by a reflex without intervention of consciousness
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