/ Dictionary / Index C castle in the air: Meaning and Definition of Find definitions for: cas'tle in the air' Pronunciation: [key] a fanciful or impractical notion or hope; daydream. Also called Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. castle castle nut Related Content Daily Word Quiz: penurious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language