vancomycinEnglishOxford Dictionary of Englishvancomycin /ˌvaŋkəˈmʌɪsɪn / ▸ noun [mass noun] Medicine a bacterial antibiotic used against resistant strains of streptococcus and staphylococcus. This antibiotic is obtained from the bacterium Streptomyces orientalis. – ORIGIN 1950s: from vanco-(of unknown origin) + -mycin.