[brain] n [ME, fr. OE braegen; akin to MLG bregen brain, and perh. to Gk brechmos front part of the head] (bef. 12c) 1 a: the portion of the vertebrate central nervous system that constitutes the organ of thought and neural coordination, includes all the higher nervous centers receiving stimuli from the sense organs and interpreting and correlating them to formulate the motor impulses, is made up of neurons and supporting and nutritive structures, is enclosed within the skull, and is continuous with the spinal cord through the foramen magnum b: a nervous center in invertebrates comparable in position and function to the vertebrate brain
2. a (1): intellect, mind "has a clever ~" (2): intellectual endowment: intelligence--often used in pl. "plenty of ~s in that family" b (1): a very intelligent or intellectual person (2): the chief planner of an organization or enterprise--usu. used in pl.
3: something that performs the functions of a brain; esp: an automatic device (as a computer) for control or computation
[2]brain vt (14c) 1: to kill by smashing the skull
2: to hit on the head