meth·​i·​cil·​lin ˌme-thə-ˈsi-lən How to pronounce methicillin (audio)
: a semisynthetic penicillin C17H19N2O6NaS used especially in the form of its sodium salt against beta-lactamase-producing staphylococci

Examples of methicillin in a Sentence

Recent Examples on the Web About 40% of those S. aureus infections were the difficult-to-treat kind: methicillin-resistant S. aureus, also known as MRSA. Isabella Cueto, STAT, 6 Feb. 2023 Microban 24 is a sanitizing spray that, according to the brand’s website, provides 24-hour protection against Staphylococcus aureus—a microbial villain that comes in several varieties, including the methicillin-resistant type known as MRSA, any of which can cause a serious staph infection. Heather Mayer Irvine, Popular Mechanics, 20 Sep. 2021 Roughly 40% of the infections were resistant to treatment with the antibiotic methicillin, the report found. Fox News, 7 Feb. 2023 Some of the most dangerous superbugs include methicillin-resistant Staphylococcus aureus (MRSA), Clostridioides difficile, carbapenem-resistant Enterobacteriaceae and Neisseria gonorrhoeae, the causative agent of gonorrhea. Bill Sullivan, Discover Magazine, 3 Nov. 2021 Young and otherwise healthy people can get a methicillin-resistant Staphylococcus aureus, or MRSA, infection on their skin., 14 July 2022

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'methicillin.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History


meth- + penicillin

First Known Use

1961, in the meaning defined above

Time Traveler
The first known use of methicillin was in 1961

Dictionary Entries Near methicillin

Cite this Entry

“Methicillin.” Dictionary, Merriam-Webster, Accessed 17 Apr. 2024.

Kids Definition


meth·​i·​cil·​lin ˌmeth-ə-ˈsil-ən How to pronounce methicillin (audio)
: a form of penicillin used especially against certain forms of staphylococcus bacteria

Medical Definition


meth·​i·​cil·​lin ˌmeth-ə-ˈsil-ən How to pronounce methicillin (audio)
: a semisynthetic penicillin C17H19N2O6NaS that is especially effective against beta-lactamase producing staphylococci
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