sulfonamide Syllabification: (sul·fon·a·mide)Pronunciation: /səlˈfänəˌmīd/ (chiefly British also sulphonamide)Definition of sulfonamide noun Medicine any of a class of synthetic drugs, derived from sulfanilamide, that are able to prevent the multiplication of some pathogenic bacteria. Origin: late 19th century: from sulfone + amidesulfonamide in other Oxford dictionaries Definition of sulfonamide in the British & World English dictionary