THROMBIN Meaning of THROMBIN in English [ 'θrɒmbɪn ]■ noun Biochemistry an enzyme in blood plasma which causes the clotting of blood by converting fibrinogen to fibrin.OriginC19: from Gk thrombos 'blood clot' + -in 1 . Concise Oxford English vocab. Сжатый оксфордский словарь английского языка. 2004