plasminogenPhysiol.|plæzˈmɪnədʒən| [f.prec. + -ogen.] The inactive precursor, present in blood, of the enzyme plasmin. 1945[see prec.].1962Lancet 27 Jan. 191/1 The presence of plasminogen activator in tissue suggests that it may have a role in the removal of unwanted fibrin.1968,1976[see prec.].