/ Dictionary / Index S Sebastian: Meaning and Definition of Find definitions for: Se•bas•tian Pronunciation: (si-bas'chun), [key] — n. dieda.d.288?, Roman martyr. a male given name. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. sebacic acid Sebastopol Related Content Daily Word Quiz: procrastinate Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language