any of a group of isomeric, antibiotic compounds with the general formula CHNOSR, obtained from the filtrates of certain molds (esp., Penicillium notatum and P. chrysogenum) or produced synthetically
Origin:
< penicillium + -in
See penicillin in American Heritage Dictionary 4
noun
Any of a group of broad-spectrum antibiotic drugs obtained from penicillium molds or produced synthetically, most active against gram-positive bacteria and used in the treatment of various infections and diseases.