\Hy`po*phos"phor*ous\, a. [Pref. hypo- +
phosphorous.] (Chem.)
Pertaining to, or containing, phosphorus in a lower state of
oxidation than in phosphoric compounds; as, hypophosphorous
acid.
{Hypophosphorous acid} (Chem.), an acid, {H3PO2}, whose salts
   are produced by the action of barium hygrate on
   phosphorus. It may be obtained from its water solution, by
   exaporation and freezing, as a white crystalline
   substance. It is a powerful reducing agent.