penicillins Definition

any of several relatively nontoxic antibiotic acids of the general formula C9H11N2O4SR that are produced by molds (genus Penicillium and especially P. notatum or P. chrysogenum) or synthetically and are used especially against gram-positive cocci; also : a mixture of such acids

a salt or ester of a penicillin or a mixture of such salts or esters