Cambridge Dictionaries online Cambridge Dictionaries online

The most popular online dictionary and thesaurus for learners of English


English definition of “penicillin”


noun [U]     /ˌpenɪˈsɪlɪn/
a type of medicine that kills bacteria and is used to treat illness Specific medicines and drugsSpecific types of drug
(Definition of penicillin noun from the Cambridge Learner's Dictionary © Cambridge University Press)

Definitions of “penicillin” in other dictionaries

Word of the Day


the art and knowledge involved in preparing and eating good food

Word of the Day


Read our blog about how the English language behaves.

Learn More

New Words

Find words and meanings that have just started to be used in English, and let us know what you think of them.

Learn More