/ Dictionary / Index P plastoquinone: Meaning and Definition of Find definitions for: plas•to•qui•none Pronunciation: (plas"tō-kwu-nōn', -kwin'ōn), [key] — n. Biochem. a quinone that occurs in the chloroplasts of plants and functions as an electron carrier during photosynthesis. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. plastometer plastotype Related Content Daily Word Quiz: nefarious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language