/ Dictionary / Index T tonoplast: Meaning and Definition of Find definitions for: ton•o•plast Pronunciation: (ton'u-plast", tō'nu-), [key] — n. Bot. a membrane separating a vacuole from the surrounding cytoplasm in a plant cell. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. tonometer tonsil Related Content Daily Word Quiz: loathe Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language