1. Any of a group of broad-spectrum antibiotics produced biosynthetically by fermentation with a strain of Streptomyces aureofaciens and certain other species or chemically by hydrogenolysis of chlortetracycline.

2. C₂₂H₂₄O₈N₂ A broad- spectrum antibiotic belonging to the tetracycline group of antibiotics; useful because of broad antimicrobial action, with low toxicity, in the therapy of infections caused by gram-positive and gram-negative bacteria as well as rickettsiae and large viruses such as psittacosis-lymphogranuloma viruses.