brain

1 of 2

noun

1
a
: 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
2
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
3
: something that performs the functions of a brain
especially : an automatic device (such as a computer) for control or computation

Illustration of brain

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

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

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.
Recent Examples on the Web
Noun
Share [Findings] Mount Vesuvius turned a Herculaneum man’s brain to glass, according to archaeologists, who also revived the voice of a priest from the reign of Ramesses XI and determined that a mummy in the Ulster Museum had been stabbed in the back. Rafil Kroll-Zaidi, Harper's Magazine, 28 Feb. 2024 If David is the brain of Curb, however, Lewis was the raw, bleeding heart, the perpetually aggrieved best friend who takes offense at even the most minor slights and breaches, who can’t help but constantly be taken aback by his friend’s emotional limitations. Ej Dickson, Rolling Stone, 28 Feb. 2024 The visual artist and digital storyteller is the brains behind @jerrygogosian, a popular Instagram meme account that satirizes and comments on the global art world through viral images, videos and text pieces. Etan Vlessing, The Hollywood Reporter, 27 Feb. 2024 These digital brains are the architects of robotic ingenuity, enabling them to solve problems and navigate complex environments with increasing autonomy. Timothy Papandreou, Forbes, 27 Feb. 2024 This means that our brains actually perceive tools as literal parts of our bodies. Chip Colwell, Smithsonian Magazine, 26 Feb. 2024 Instead, healthcare providers must often use tests to rule out other conditions, or order imaging tests like MRIs for the brain. Julia Landwehr, Health, 26 Feb. 2024 Some that can be fatal, require brain surgery or removal of adrenal glands. Nardine Saad, Los Angeles Times, 26 Feb. 2024 Puig, a popular star soccer player at Lourdes, survived but with severe brain damage. David Goodhue, Miami Herald, 16 Feb. 2024
Verb
And Daryl, of course, is defined in part by the death of Merle and having brained Merle. Dalton Ross, EW.com, 16 Oct. 2023 Bird brains With a population of over 27 million and counting, crows seem almost ubiquitous across the US. Kenna Hughes-Castleberry, Ars Technica, 13 Sep. 2023 The new technique, transplant surgeons say, significantly expands the potential pool to patients who are comatose but not brain dead, and whose families have withdrawn life support because there is little chance of recovery. Joseph Goldstein, New York Times, 22 Nov. 2023 Neanderthal Brain Size Overall, these skulls indicate that the brains of H. neanderthalensis and H. sapiens were similarly sized, with H. neanderthalensis brains beating H. sapiens brains only slightly in terms of their total volume. Sam Walters, Discover Magazine, 1 Mar. 2023 Companies will also have to make sure their chatbots create words and pictures that are truthful and respect intellectual property, and will be required to register their algorithms, the software brains behind chatbots, with regulators. Chang Che, New York Times, 24 Apr. 2023 So can brain injuries and tumors. Carl Zimmer, Discover Magazine, 4 Dec. 2014 Thanks to producer PJ Elliott for his great work on the show, and be sure to tune in tomorrow when PJ speaks with Health reporter, Karen Weintraub about the latest organ transplant milestone: pig hearts to brain dead patients. Taylor Wilson, USA TODAY, 13 July 2022 Internet connections can be wireless, so why shouldn’t brain medicine be? Elizabeth Preston, Discover Magazine, 2 Dec. 2015 See More

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'brain.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

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

Dictionary Entries Near brain

Cite this Entry

“Brain.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/brain. Accessed 4 Mar. 2024.

Kids Definition

brain

1 of 2 noun
1
a
: 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
b
: the main nervous center in an invertebrate animal
2
a
: intelligence sense 1
often used in plural
plenty of brains in that family
b
: a very intelligent person
brainlike adjective

brain

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

Medical Definition

brain

noun
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

More from Merriam-Webster on brain

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