brain / head / chief, principal

(neuroanatomy) rhinencephalon

(anatomy) the brain / (by extension, figuratively) one's brains, one's mental functioning

(archaic, anatomy) the brain / (archaic, by extension) the head

brain; brains / mind; intellect; understanding

brain cancer

gyrus (a ridge or fold on the cerebral cortex)

intracerebral; intracranial; the inside of the head / (figuratively) the inside of one's mind; within one's mind; mental (of imagined things, etc.)

(Internet slang) person who inflames public anxiety and/or fear with groundless information about radioactivity.

(slang) meathead; dumb muscle; someone that often uses physical strength without thinking