glutathione Syllabification: (glu·ta·thi·one)Pronunciation: /ˌglo͞otəˈTHīōn/Definition of glutathione noun Biochemistry a compound involved as a coenzyme in oxidation-reduction reactions in cells. It is a tripeptide derived from glutamic acid, cysteine, and glycine. glutathione in other Oxford dictionaries Definition of glutathione in the British & World English dictionary