Breadcrumb Home > Dictionary > Index T thymosin: Meaning and Definition of Find definitions for: thy•mo•sin Pronunciation: (thī'mu-sin), [key] — n. Biochem. a hormone, produced by the thymus gland, that promotes the development of T cells from stem cells. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: thymosin (Thesaurus) thymol thymus ✖ Related Content Daily Word Quiz: quadrumanous Analogy of the Day: Today’s Analogy Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language