Phosphonic \Phos*phon"ic\ (f[o^]s*f[o^]n"[i^]k), a. [Phosphoric
+ sulphonic.] (Chem.)
Pertaining to, or designating, certain derivatives of
phosphorous acid containing a hydrocarbon radical with the
phosphorus directly bonded to a carbon, and analogous to the
sulphonic acids; as, methanephosphonic acid, {CH3.PO.(OH)2}.
[1913 Webster + PJC]