/ Dictionary / Index P piperonal: Meaning and Definition of Find definitions for: pi•per•o•nal Pronunciation: (pi-per'u-nal", pī-, pip'ur-u-), [key] — n. Chem. a white, crystalline, water-insoluble aldehyde, CHO, which darkens on exposure to light: used chiefly in perfumery and organic synthesis. Also called Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. piperine piperonyl butoxide Related Content Daily Word Quiz: penchant Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language