The Collaborative International Dictionary
H3PO3
Phosphorous \Phos"phor*ous\ (f[o^]s"f[o^]r*[u^]s), a. [Cf. F. phosphoreux.] (Chem.) Of or pertaining to phosphorus; resembling or containing phosphorus; specifically, designating those compounds in which phosphorus has a lower valence as contrasted with phosphoric compounds; as, phosphorous acid, H3PO3.