/ Dictionary / Index T thionyl: Meaning and Definition of Find definitions for: thi•o•nyl Pronunciation: (thī'u-nil), [key] — adj. Chem. sulfinyl. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. thionic acid thionyl chloride Related Content Daily Word Quiz: eureka Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language