hypophosphoric

from Wiktionary, Creative Commons Attribution/Share-Alike License

• adj. Of or pertaining to hypophosphoric acid or its derivatives

from the GNU version of the Collaborative International Dictionary of English

• adj. Pertaining to, or derived from, or containing, phosphorus in a lower state of oxidation than in phosphoric compounds.

from The Century Dictionary and Cyclopedia

• Same as hypophosphorous.
• Noting an acid, a distinct tetra basic acid, H4P2O6, produced, along with phosphorous and phosphoric acids, by the slow oxidation of phosphorus in moist air at ordinary temperatures.