eryth·ro·my·cin \ə̇ˌrithrəˈmīsən\noun (-s) Etymology:erythr- + -mycin : a broad-spectrum antibiotic produced by a bacterium of the genus Streptomyces (S. erythreus), resembling penicillin in antibacterial activity, and effective also against amoebas, treponemata, and pinworms