/ Dictionary / Index S sulfonic acid: Meaning and Definition of Find definitions for: sulfon'ic ac'id Pronunciation: [key] — Chem. Chem. any of a large group of organic compounds of the structure RSOOH, which are strong acids that give neutral sodium salts: used in the synthesis of phenols, dyes, and other substances. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. sulfonic sulfonium 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