/ Dictionary / Index S semisynthetic: Meaning and Definition of Find definitions for: sem•i•syn•thet•ic Pronunciation: (sem"ē-sin-thet'ik, sem"ī-), [key] — adj. Chem. derived synthetically from one or more substances of natural origin. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: semisynthetic (Thesaurus) semisweet Semite 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