/ Dictionary / Index M midbrain: Meaning and Definition of Find definitions for: mid•brain Pronunciation: (mid'brān"), [key] — n. Anat. the middle of the three primary divisions of the brain in the embryo of a vertebrate or the part of the adult brain derived from this tissue; mesencephalon. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: midbrain (Thesaurus) midband Mid-Cities Related Content Daily Word Quiz: panacea Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language