[pen.i.cil.lin] n [NL Penicillium] (1929) 1: any of several relatively nontoxic antibiotic acids that are produced by molds (genus Penicillium and esp. P. notatum or P. chrysogenum) or synthetically and are used esp. against cocci; also: a mixture of such acids
2: a salt or ester of a penicillin or a mixture of such salts or esters