guanosine Syllabification: (gua·no·sine)Pronunciation: /ˈgwänəˌsēn/Definition of guanosine noun Biochemistry a compound consisting of guanine combined with ribose, a nucleoside unit in RNA. Origin: early 20th century: from guanine, with the insertion of -ose2guanosine in other Oxford dictionaries Definition of guanosine in the British & World English dictionary