/ Dictionary / Index T thrombin: Meaning and Definition of Find definitions for: throm•bin Pronunciation: (throm'bin), [key] — n. Biochem. an enzyme of the blood plasma that catalyzes the conversion of fibrinogen to fibrin, the last step of the blood clotting process. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: thrombin (Thesaurus) thrombectomy thrombo- Related Content Daily Word Quiz: panacea Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language