bi·gua·nide \(ˈ)bī|gwäˌnīd, -_nə̇d\noun (-s) Etymology: International Scientific Vocabulary bi- (I) + guan- (from guanidine) + -ide : a strong amorphous base NH[C( = NH)NH2]2 some of whose derivatives (as aryl derivatives) find use as antimalarial drugs or as precipitants for dyes in color photography