methemoglobin Syllabification: (meth·e·mo·glo·bin)Pronunciation: /metˈhēməˌglōbən/ (Britishmethaemoglobin)Definition of methemoglobin noun Biochemistry a stable oxidized form of hemoglobin that is unable to release oxygen to the tissues, produced in some inherited abnormalities and by oxidizing drugs. methemoglobin in other Oxford dictionaries Definition of methemoglobin in the British & World English dictionary