/ Dictionary / Index B ballon d'essai*: Meaning and Definition of Find definitions for: bal•lon d'es•sai Pronunciation: (ba-lôn de-se'), [key] — pl. bal•lons d'es•sai See(def. 1). Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. ballon ballonet Related Content Daily Word Quiz: diurnal Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language