/ Dictionary / Index C crackbrain: Meaning and Definition of Find definitions for: crack•brain Pronunciation: (krak'brān"), [key] — n. a foolish, senseless, or insane person. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. crackajack crackbrained Related Content Daily Word Quiz: languid Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language