\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}.