haptoglobin Syllabification: (hap·to·glo·bin)Pronunciation: /ˌhaptəˈglōbən/Definition of haptoglobin noun Biochemistry a protein present in blood serum that binds to and removes free hemoglobin from the bloodstream. Origin: 1940s: from Greek haptein 'fasten' + (hemo)globinhaptoglobin in other Oxford dictionaries Definition of haptoglobin in the British & World English dictionary