Source : Webster's Revised Unabridged Dictionary (1913)

Hyposulphurous \Hy`po*sul"phur*ous\, a. [Pref. hypo- +
   sulphurous.] (Chem.)
   Pertaining to, or containing, sulphur, all, or a part, in a
   low state of oxidation.

   {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}.