erythromycin: an antibiotic (trade name Erythrocin or E-Mycin or Ethril or Ilosone or Pediamycin) obtained from the actinomycete Streptomyces erythreus; effective against many Gram-positive bacteria and some Gram-negative
antibiotic: a chemical substance derivable from a mold or bacterium that can kill microorganisms and cure bacterial infections