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 In addition to Belgica antarctica, the terrestrial ecosystem is composed of just a handful of small animals like springtails (a type of tiny arthropod), a smattering of microorganisms and low-lying ground cover such as lichen. Popular Science, 15 Feb. 2024 Cordero doesn’t know what the analogous traits might be for microorganisms and their communities. Dan Samorodnitsky, Quanta Magazine, 17 Jan. 2024 The air inside circulates through UV light, which kills bacteria and other microorganisms. Ann Maloney, Washington Post, 28 Mar. 2024 Farmers like 62-year-old Orlando Morales living near the mines complain of smaller crop yields. Flamingos, feeding on microorganisms within the brine, have slowly been killed off by mining, a 2022 study showed. Megan Janetsky, Victor R. Caivano and Rodrigo Abd, Quartz, 13 Mar. 2024 These microorganisms also help regulate inflammation and other aspects of immune functioning. Markham Heid, TIME, 9 Feb. 2024 To complicate things further, Moorthy adds how bacteria and viruses can live on different surfaces for different times, and some foods seem to attract microorganisms more easily than others. Brittany Edelmann, Discover Magazine, 3 Jan. 2024 On the line was Jillian Banfield, a microbiologist on campus whose lab had developed a method to sequence the DNA of all the microorganisms living in a pinch of soil or an acidic drop of mine drainage. Megan Molteni, STAT, 21 Feb. 2024 Baum explained that this can happen when microorganisms enter an environment with optimal conditions for growing and dividing. Jocelyn Solis-Moreira, CNN, 5 Feb. 2024

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

Word History


International Scientific Vocabulary

First Known Use

1880, in the meaning defined above

Time Traveler
The first known use of microorganism was in 1880

Dictionary Entries Near microorganism

Cite this Entry

“Microorganism.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/microorganism. Accessed 24 Apr. 2024.

Kids Definition


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


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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