Main Entry: ¹brain

Pronunciation: \ˈbrān\

Function: noun

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

Date: before 12th century

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 (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 — 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 (as a computer) for control or computation

[brain illustration]