cuprammoniumPronunciation: /ˌkjuːprəˈməʊnɪəm/Definition of cuprammonium noun [as modifier] Chemistry a complex ion, Cu(NH3)42+, formed in solution when ammonia is added to copper salts. The solution is deep blue and is used to dissolve cellulose. cuprammonium in other Oxford dictionaries Definition of cuprammonium in the US English dictionary