any of a group of antibiotics with powerful bactericidal action, used to treat many types of infections, including pneumonia, gonorrhoea, and infections caused by streptococci and staphylococci: originally obtained from the fungus Penicillium, esp P. notatum. Formula: R-C9H11N2O4S where R is one of several side chains
WordReference Random House Learner's Dictionary of American English © 2026
pen•i•cil•lin /ˌpɛnəˈsɪlɪn/USA pronunciation
n. [uncountable]
WordReference Random House Unabridged Dictionary of American English © 2026- Drugsan antibiotic produced from molds.
pen•i•cil•lin
(pen′ə sil′in),USA pronunciation n. [Pharm.]
- Drugsany 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.
- penicill(ium) + -in2 1925–30
Collins Concise English Dictionary © HarperCollins Publishers::
'penicillin' also found in these entries (note: many are not synonyms or translations):
-in
- Chain
- Fleming
- acetanilide
- amoxicillin
- ampicillin
- antibiotic
- carbenicillin
- cephalexin
- cloxacillin
- discover
- erythromycin
- injectant
- lincomycin
- methicillin
- mezlocillin
- oxacillin
- penicillamine
- penicillium
- pentyl acetate
- phenylacetic acid
- piperacillin