microorganism

noun

mi·​cro·​or·​gan·​ism ˌmī-krō-ˈȯr-gə-ˌni-zəm How to pronounce microorganism (audio)
: an organism (such as a bacterium or protozoan) of microscopic or ultramicroscopic size

Examples of microorganism in a Sentence

Recent Examples on the Web
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
Plastics, microplastics and toxic chemicals can hurt and kill the microorganisms that make his compost healthy and valued. Los Angeles Times, 4 July 2025 The gut microbiota is the set of microorganisms that live in our intestines, performing a number of actions that have a direct impact on skin tissue. Violeta Valdés, Vogue, 2 July 2025 The vitality of the microorganisms present determines the ultimate success of the pile, and an overly acidic environment can disrupt their activity. Anthony Reardon, Kansas City Star, 27 June 2025 In the last several years, researchers have discovered that living beings contribute more to Earth’s clouds than expected thanks to gases from plants and plankton, and sea spray that propels microorganisms and proteins skyward. Max G. Levy, Smithsonian Magazine, 26 June 2025 See All Example Sentences for microorganism

Word History

Etymology

International Scientific Vocabulary

First Known Use

1880, in the meaning defined above

Time Traveler
The first known use of microorganism was in 1880

Browse Nearby Words

Cite this Entry

“Microorganism.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/microorganism. Accessed 13 Jul. 2025.

Kids Definition

microorganism

noun
mi·​cro·​or·​gan·​ism ˌmī-krō-ˈȯr-gə-ˌniz-əm How to pronounce microorganism (audio)
: an organism (as a bacterium) of microscopic or less than microscopic size

Medical Definition

microorganism

noun
mi·​cro·​or·​gan·​ism -ˈȯr-gə-ˌniz-əm How to pronounce microorganism (audio)
: an organism of microscopic or ultramicroscopic size

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