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.
Both are touted as drinks that can reduce bloating, aid in digestion, and even help support the good microorganisms in your gastrointestinal tract. — Sherri Gordon, HEALTH, 1 Sep. 2026 From there, Adenot headed off to continue an ongoing scientific study by swabbing areas on the exterior of the airlock and her gloves for possible microorganisms. — Robert Z. Pearlman, Space.com, 1 Sep. 2026 Harrison added that the recall has nothing to do with an allergen, microorganism or pathogen contamination. — Saleen Martin, USA Today, 31 Aug. 2026 Hydrogen Peroxide Works Better in the Dark Conventional wisdom suggests cleaning in the warm heat of natural sunlight to kill bacteria and other microorganisms. — Michelle Mastro, The Spruce, 31 Aug. 2026 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

Rhymes for microorganism

See All Rhymes for microorganism

Browse Nearby Words

micronutrient
microorganism
micropaleontological
See all Nearby Words

Cite this Entry

“Microorganism.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/microorganism. Accessed 4 Sep. 2026.

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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

More from Merriam-Webster on microorganism

Britannica.com: Encyclopedia article about microorganism

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