The Collaborative International Dictionary
Sulphophosphoric
Sulphophosphoric \Sul`pho*phos*phor"ic\, a. Of, pertaining to, or designating, a hypothetical sulphacid of phosphorus, analogous to phosphoric acid, and known in its salts.
Wiktionary
sulphophosphoric
a. (context chemistry English) Of, pertaining to, or designating a hypothetical thioacid of phosphorus, analogous to phosphoric acid, and known only in its salts.