Dictionary
pen•i•cil•lin
Pronunciation: (pen"u-sil'in), [key]—
n. Pharm.
any of several antibiotics of low toxicity, produced naturally by molds of the genus
Penicillium and also semisynthetically, having a bactericidal action on many susceptible Gram-positive or Gram-negative cocci and bacilli, some also being effective against certain spirochetes.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.