mid·​brain | \ ˈmid-ˌbrān \

Definition of midbrain

: the middle of the three primary divisions of the developing vertebrate brain or the corresponding part of the adult brain between the forebrain and hindbrain that includes the tectum, tegmentum, and substantia nigra

called also mesencephalon

— see brain illustration

Examples of midbrain in a Sentence

Recent Examples on the Web

Characterized by muscle stiffness and tremors, Parkinson's is caused by the death of dopamine-producing neurons in a section of the midbrain. Ferris Jabr, Scientific American, "How the Brain Gets Addicted to Gambling," 14 May 2018 One set of axons projected to the periacqueductal gray in the midbrain, an area involved in motor behaviors. Lydia Denworth, Scientific American, "A Command Center in the Mammalian Brain Orchestrates Parenting Behaviors," 11 Apr. 2018

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

First Known Use of midbrain

1864, in the meaning defined above

Keep scrolling for more

Learn More about midbrain

Statistics for midbrain

Look-up Popularity

Time Traveler for midbrain

The first known use of midbrain was in 1864

See more words from the same year

Keep scrolling for more

More Definitions for midbrain


mid·​brain | \ ˈmid-ˌbrān \

Medical Definition of midbrain

: the middle division of the three primary divisions of the developing vertebrate brain or the corresponding part of the adult brain that includes a ventral part containing the cerebral peduncles and a dorsal tectum containing the corpora quadrigemina and that surrounds the aqueduct of Sylvius connecting the third and fourth ventricles

called also mesencephalon

More from Merriam-Webster on midbrain

Rhyming Dictionary: Words that rhyme with midbrain

Britannica.com: Encyclopedia article about midbrain

Comments on midbrain

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


someone who never drinks alcohol

Get Word of the Day daily email!

Test Your Vocabulary

Homophone Quiz

  • three-bears-two-of-them-look-like-theyre-whispering-to-a-third-bear-who-looks-chuffed-to-be-the-center-of-attention
  • In order to judge how people felt, the senator's office hired a firm to take a ______.
Spell It

Can you spell these 10 commonly misspelled words?


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


Love words? Need even more definitions?

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