1.NounAn aminoglycoside and bactericidal antibiotic C21H39N7O12 that is produced by a soil actinomycete (Streptomyces griseus), is active against many bacteria, and is administered via intramuscular injection especially in the treatment of infections by gram-negative bacteria. It was the first drug to be successful against tuberculosis but is now chiefly used with other drugs because of its toxic side effects.