dithionite Syllabification: (di·thi·o·nite)Pronunciation: /dīˈTHīəˌnīt/Definition of dithionite noun Chemistry a salt containing the anion S2O42. Origin: mid 20th century: from di-1 'two' + Greek theion 'sulfur' + -ite1dithionite in other Oxford dictionaries Definition of dithionite in the British & World English dictionary