reflex

1 of 2

noun

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

reflex

2 of 2

adjective

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

Noun

He’s got good hands and reflexes on tips and redirects around the net. —Scott Wheeler, The Athletic, 13 Feb. 2025

Each mode will test your reflexes and aim – and thankfully, there aren't a ton of rules to memorize. —New Atlas, 9 Feb. 2025

Adjective

Common triggers include dehydration from illness, vasovagal syncope—a reflex response to nausea or pain—abnormal heart rhythms, and heart valve conditions such as aortic stenosis. —Thomas G. Moukawsher, Newsweek, 6 Feb. 2025

The reflex reaction might well be, What exactly have the governor and fellow Democrats been doing for the previous six years? —The Editorial Board, Chicago Tribune, 4 Feb. 2025

Word History

Etymology

Noun

Latin reflexus, past participle of reflectere to reflect

Adjective

Latin reflexus

First Known Use

Noun

1508, in the meaning defined at sense 1a

Adjective

1607, in the meaning defined at sense 1

Phrases Containing reflex

• Babinski reflex
• Babinski's reflex
• reflex arc
• reflex sympathetic dystrophy
• single-lens reflex

Kids 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