brain

1 of 2

noun

ˈbrān

: the portion of the vertebrate central nervous system enclosed in the skull and continuous with the spinal cord through the foramen magnum that is composed of neurons and supporting and nutritive structures (such as glia) and that integrates sensory information from inside and outside the body in controlling autonomic function (such as heartbeat and respiration), in coordinating and directing correlated motor responses, and in the process of learning compare forebrain, hindbrain, midbrain

: a nervous center in invertebrates comparable in position and function to the vertebrate brain

a(1)

: intellect, mind

has a clever brain

(2)

: intellectual endowment : intelligence

—often used in plural

plenty of brains in that family

b(1)

: a very intelligent or intellectual person

(2)

: the chief planner within a group

—usually used in plural

she's the brains behind their success

: something that performs the functions of a brain

especially : an automatic device (such as a computer) for control or computation

Illustration of brain

1 cerebral hemisphere
2 corpus callosum
3 ventricle
4 fornix
5 thalamus
6 pituitary gland
7 pons
8 medulla oblongata
9 spinal cord
10 cerebellum
11 midbrain

brain

2 of 2

verb

brained; braining; brains

transitive verb

: to kill by smashing the skull

: to hit on the head

Example Sentences

Noun Scientists are learning more about how the human brain works. The left and right sides of the brain have different functions. The other children always teased him about being such a brain. Verb The tree limb fell and nearly brained me.

Recent Examples on the Web

Noun

The film homes in on the relationship between a military engineer (Lawrence) recovering from the effects of a severe brain injury and an auto repair shop mechanic (Henry) living with the guilt and the physical aftereffects of a car accident. —

Nardos Haile, Anchorage Daily News, 25 Jan. 2023 The film homes in on the relationship between a military engineer (Lawrence) recovering from the effects of a severe brain injury and an auto repair shop mechanic (Henry) living with the guilt and the physical aftereffects of a car accident. —

Nardos Haile, ajc, 24 Jan. 2023 Hull noted in the 2019 documents the following injuries for the Enzo - head trauma, closed head trauma, brain injury, hypoxic ischemic encephalopathy, multiple retinal hemorrhages and multiple contusions to the head and body. —

Carol Robinson | Crobinson@al.com, al, 24 Jan. 2023 Judy Guinn, a pediatrician who specializes in child abuse cases, examined the infant and diagnosed the child with a brain injury, hemorrhaging, rib fractures, a liver laceration, bruising to the chest and other injuries. —

Ashley Luthern, Journal Sentinel, 20 Jan. 2023 The human steamroller who spent his last few years suffering from dementia likely caused by a traumatic brain injury summoned his faculties to honor one of his successors. —

Los Angeles Times, 20 Jan. 2023 Cayden Winstead's life has been anything but easy since suffering a severe, life-threatening brain injury last February. —

Ana Rocío Álvarez Bríñez, The Courier-Journal, 18 Jan. 2023 Ma, 61, suffered a traumatic brain injury from the 2021 attack and never regained consciousness. —

Chantal Da Silva, NBC News, 13 Jan. 2023 Today, the 2-year-old breathes with the aid of a tracheostomy and ventilator as a result of a brain injury. —

Ashley R. Williams, USA TODAY, 12 Jan. 2023

Verb

Internet connections can be wireless, so why shouldn’t brain medicine be? —

Elizabeth Preston, Discover Magazine, 2 Dec. 2015 The cancer initiative is personal for Biden, who lost his son Beau Biden to brain cancer in 2015. —

Alexander Thompson, BostonGlobe.com, 11 Sep. 2022 The man who could brain Mr. Lingk with Rusty’s ashes, or the one who could harm and tie up a helpless old lady, would almost certainly be game for something that nasty. —

Alan Sepinwall, Rolling Stone, 9 Aug. 2022 This can help alleviate back and neck stress and give your eyes and brain a break from the screen. —

Alexa Mikhail, Fortune, 28 July 2022 They are linked to brain developmental problems in infants and cancer. —

Katy Stech Ferek, WSJ, 31 Jan. 2022 How will brain stimulation become accessible to all the patients who need it, given how expensive and invasive some treatments are? —

Isabella Cueto, STAT, 14 Jan. 2022 The researchers contend that this study marks the first time that a machine-learning algorithm has been matched to brain data to explain the workings of a high-level cognitive task. —

Anna Blaustein, Scientific American, 26 Oct. 2021 Arguably, achieving universal health care and higher education and addressing the nation’s aging water pipe infrastructure (which has yielded a modern-day lead crisis) could be expected to make similar contributions to brain health across decades. —

Daniel R. George, Scientific American, 25 Aug. 2021 See More

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'brain.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

Word History

Etymology

Noun

Middle English, from Old English brægen; akin to Middle Low German bregen brain, and perhaps to Greek brechmos front part of the head

First Known Use

Noun

before the 12th century, in the meaning defined at sense 1a

Verb

14th century, in the meaning defined at sense 1

Time Traveler

The first known use of brain was before the 12th century

See more words from the same century

Cite this Entry

Style

“Brain.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/brain. Accessed 2 Feb. 2023.

Copy Citation

Kids Definition

brain

1 of 2 noun

ˈbrān

: the portion of the central nervous system of vertebrate animals that is the organ of thought and the central control point for the nervous system, is enclosed within the skull, and is continuous with the spinal cord

: the main nervous center in an invertebrate animal

: intelligence sense 1

—often used in plural

plenty of brains in that family

: a very intelligent person

brainlike adjective

brain

2 of 2 verb

: to kill by smashing the skull

: to hit on the head

Medical Definition

brain

noun

ˈbrān

: the portion of the vertebrate central nervous system enclosed in the skull and continuous with the spinal cord through the foramen magnum that is composed of neurons and supporting and nutritive structures (as glia) and that integrates sensory information from inside and outside the body in controlling autonomic function (as heartbeat and respiration), in coordinating and directing correlated motor responses, and in the process of learning see forebrain, hindbrain, midbrain

: a nervous center in invertebrates comparable in position and function to the vertebrate brain