/ Dictionary / Index L left brain: Meaning and Definition of Find definitions for: left' brain' Pronunciation: [key] the cerebral hemisphere on the left side of the corpus callosum, controlling activity on the right side of the body: in humans, usually showing some degree of specialization for language and calculation. Cf. right brain. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Left Bank left-branching Related Content Daily Word Quiz: arboreal Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language