/ Dictionary / Index P phthalin: Meaning and Definition of Find definitions for: phthal•in Pronunciation: (thal'in, fthal'-), [key] — n. Chem. any of a group of compounds obtained by the reduction of the phthaleins. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. phthalic anhydride phthalocyanine Related Content Daily Word Quiz: careening Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language