Breadcrumb Home > Dictionary > Index S sinusitis: Meaning and Definition of Find definitions for: si•nus•i•tis Pronunciation: (sī"nu-sī'tis), [key] — n. Pathol. inflammation of a sinus or the sinuses. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: sinusitis (Thesaurus) Sinus Iridum Sinus Meridianii ✖ Related Content Daily Word Quiz: donnybrook Analogy of the Day: Today’s Analogy Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language