a. [ Pref. hypo- + sulphurous. ] (Chem.) Pertaining to, or containing, sulphur, all, or a part, in a low state of oxidation. [ 1913 Webster ]

Hyposulphurous acid. (a) Thiosulphuric acid. [ Obs. ] (b) An acid, H2SO2, obtained by the reduction of sulphurous acid. It is not obtained in the free state, but in an orange-yellow water solution, which is a strong reducing and bleaching agent. Called also hydrosulphurous acid. [ 1913 Webster ]