brain

noun
\ ˈbrān How to pronounce brain (audio) \

Definition of brain

 (Entry 1 of 2)

1a : 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
b : a nervous center in invertebrates comparable in position and function to the vertebrate brain
2a(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
3 : something that performs the functions of a brain especially : an automatic device (such as a computer) for control or computation

brain

verb
brained; braining; brains

Definition of brain (Entry 2 of 2)

transitive verb

1 : to kill by smashing the skull
2 : to hit on the head

Illustration of brain

Illustration of brain

Noun

brain 1a: 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

In the meaning defined above

Keep scrolling for more

Examples of brain in a Sentence

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.
See More

Recent Examples on the Web: Noun

In the four, rotating the field effected their brain's alpha frequency, known as an α frequency. David Grossman, Popular Mechanics, "Some Humans Can Detect the Earth's Magnetic Field," 19 Mar. 2019 The life-threatening infection started in his ear canal and ended up spreading to the lining of his brain after years of struggling with ear pain and hearing loss issues but not knowing the root of the problem. Kaleigh Fasanella, Allure, "A Man Developed a Near-Fatal Infection in His Brain Lining After Using a Cotton Swab," 15 Mar. 2019 Our brains can keep track of short bursts of time like a mental stopwatch. Brianna Abbott, WSJ, "Unlocking Secrets of Memory and Time in the Brain," 13 Mar. 2019 Be sure to follow PCWorld on Facebook, YouTube, and Twitch to watch future episodes live and pick our brains in real time! Gordon Mah Ung, PCWorld, "Full Nerd Special Edition: AMD talks Radeon VII and FreeSync vs. G-Sync," 4 Feb. 2019 After emergency care, recovery typically involves rehabilitating any function lost due to brain tissue damage, including changes to speech, movement, and sensation. Caroline Picard, Good Housekeeping, "Luke Perry of 'Beverly Hills, 90210' and 'Riverdale' Is Hospitalized After Suffering a Stroke," 28 Feb. 2019 After that, the trainee lies down and an electrode is attached to his forehead and finger for an omega brain-wave reading. Joe Pappalardo, Popular Mechanics, "The Air Force Is Changing How Special Ops Fighters Are Trained," 12 Feb. 2019 Most people recover after a few days but severe cases can involve brain swelling, and in extremely rare cases, death. Macaela Mackenzie, Glamour, "Rift Valley Fever Could Be the Next Global Health Crisis For Pregnant Women," 10 Jan. 2019 For the necktie study, researchers at the University Hospital Schleswig-Holstein in Germany scanned the brains of 30 men, half of whom wore neckties. Laura Newberry, latimes.com, "Citing health study, Lancaster mayor wants to ban workplace necktie requirements for city employees," 12 July 2018

Recent Examples on the Web: Verb

And yet the story rolls on, oblivious and hare-brained. John Anderson, WSJ, "‘The Romanoffs’ Review: Far From Revolutionary," 11 Oct. 2018 According to the study, the ratio of neurons to brain size in most carnivores was nearly equivalent to herbivores. Elly Belle, Teen Vogue, "Study Says Dogs Are Actually Smarter Than Cats," 18 June 2018 Took out Isadora Duncan when her scarf got caught in the spokes of a wheel, decapitated Jayne Mansfield, sprayed John Kennedy’s brains all over his wife. Aaron Gilbreath, Longreads, "The Red Caddy," 24 Apr. 2018 At least 64 people perished during the storm, drowned in their houses or brained by flying debris. The Economist, "America has let down its Puerto Rican citizens," 12 Apr. 2018 Yet if there’s a British stereotype of American English as twangy and slangy, there’s a corresponding American stereotype of British English as quaint and feather-brained. Henry Hitchings, WSJ, "‘The Prodigal Tongue’ Review: More Trouble in the Colonies," 12 Apr. 2018 Today’s condom challenge will morph into tomorrow’s equally hare-brained idea. Heidi Stevens, chicagotribune.com, "Calm down about the condom challenge, grown-ups," 2 Apr. 2018 Many experts believe that maintaining physical fitness can help keep blood flowing normally to brain tissue, which can reduce the risk of damage or deterioration. Amanda Macmillan, Time, "How Exercise May Help Protect Your Brain From Cognitive Decline and Dementia," 16 Feb. 2018 But Scotti falls back on the same old, tired, lizard-brained and misogynistic argument that people used against Hillary Clinton: That ambitious women are off-putting. Madeleine Aggeler, The Cut, "When Will We Stop Shaming Ambitious Women?," 5 Jan. 2018

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.

See More

First Known Use of brain

Noun

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

Verb

14th century, in the meaning defined at sense 1

History and Etymology for brain

Noun

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

Keep scrolling for more

Learn More about brain

Statistics for brain

Last Updated

23 Mar 2019

Look-up Popularity

Time Traveler for brain

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

See more words from the same century

Keep scrolling for more

More Definitions for brain

brain

noun

English Language Learners Definition of brain

 (Entry 1 of 2)

: the organ of the body in the head that controls functions, movements, sensations, and thoughts
informal : the ability to think and reason
informal : a very intelligent person

brain

verb

English Language Learners Definition of brain (Entry 2 of 2)

informal : to hit (someone) on the head very hard

brain

noun
\ ˈbrān How to pronounce brain (audio) \

Kids Definition of brain

 (Entry 1 of 2)

1 : the part of the nervous system that is inside the skull, consists of grayish nerve cells and whitish nerve fibers, and is the organ of thought and the central control point for the nervous system
2 : the ability to think : intelligence
3 : someone who is very smart

brain

verb
brained; braining

Kids Definition of brain (Entry 2 of 2)

: to hit on the head very hard

brain

noun
\ ˈbrān How to pronounce brain (audio) \

Medical Definition of brain

1 : 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
2 : a nervous center in invertebrates comparable in position and function to the vertebrate brain

Keep scrolling for more

More from Merriam-Webster on brain

Rhyming Dictionary: Words that rhyme with brain

Thesaurus: All synonyms and antonyms for brain

Spanish Central: Translation of brain

Nglish: Translation of brain for Spanish Speakers

Britannica English: Translation of brain for Arabic Speakers

Britannica.com: Encyclopedia article about brain

Comments on brain

What made you want to look up brain? Please tell us where you read or heard it (including the quote, if possible).

WORD OF THE DAY

grandiloquent, ostentatious, or bombastic

Get Word of the Day daily email!

Test Your Vocabulary

Original Meanings Quiz

  • rembrandt-painting-a-young-scholar-and-his-tutor
  • Which of the following is the earliest known sense of the word awe?
How Strong Is Your Vocabulary?

Test your vocabulary with our 10-question quiz!

TAKE THE QUIZ
Word Winder's CrossWinder

Test Your Knowledge - and learn some interesting things along the way.

TAKE THE QUIZ

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!