/ Dictionary / Index L lactone: Meaning and Definition of Find definitions for: lac•tone Pronunciation: (lak'tōn), [key] — n. Chem. any of a group of internal esters derived from hydroxy acids. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. lactometer lactonize Related Content Daily Word Quiz: rustic Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language