/ Dictionary / Index S sulfoxide: Meaning and Definition of Find definitions for: sulf•ox•ide Pronunciation: (sul-fok'sīd) [key] — n. Chem. a brown liquid, CHOS, insoluble in water, used as an insecticide synergist. any of the compounds with the radical =SO, as dimethyl sulfoxide, (CH)SO. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. sulfo radical sulfur Related Content Daily Word Quiz: quandary Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language