mi·​cro·​or·​gan·​ism | \ -ˈȯr-gə-ˌni-zəm How to pronounce microorganism (audio) \

Definition of microorganism

: an organism (such as a bacterium or protozoan) of microscopic or ultramicroscopic size

Examples of microorganism in a Sentence

Recent Examples on the Web

This important balance of microorganisms is also known as your skin microbiome. Jessica Toscano, SELF, "Here’s How Often You Should Really Be Washing Your Sheets," 23 Feb. 2019 The curators liken his frames to stem cells, which can regenerate into different kinds of microorganisms. Lane Florsheim, WSJ, "130,000 Andy Warhol Photos, Once Unknown, Debut in a New Exhibition in California," 27 Sep. 2018 But equally important is how the off-earth environment impacts the microorganisms in our bodies and all around us. John Wenz, Popular Mechanics, "Living in Space Doesn't Turn Bacteria into Killer Superbugs, Study Says," 9 Jan. 2019 The eczema study is the latest in a flood of research in the past several years on the skin microbiome—the microscopic ecosystem containing trillions of bacteria, fungi, viruses and other microorganisms that live on our skin—showing how... Susan Kitchens, WSJ, "Bacteria May Offer New Hope for Treating Skin Disorders," 5 Feb. 2019 Most of the lifeforms discovered are bacteria and other single-cell microorganisms, such as archaea, but their sheer mass equals roughly 15 to 23 billion tonnes of carbon—more than humanity's total imprint on the surface. Sam Blum, Popular Mechanics, "Vast Ecosystem of Underground Organisms Holds More Life Than Earth's Oceans," 11 Dec. 2018 This allows the ice to absorb more solar energy, thereby heating up and melting faster, which in turn allows the microorganisms to spread further. Umair Irfan, Vox, "Greenland’s ice sheet is melting at its fastest rate in centuries," 8 Dec. 2018 But the microorganisms inhabiting our intestines have no such problems. SELF, "Why This Registered Dietitian Tells (Some of) Her Patients to Avoid Kale Salads," 30 Nov. 2018 Pulling It Together Pathogens hitch rides on hosts, spreading microorganisms such as bacteria and viruses. Mallory Locklear, Discover Magazine, "With Big Data and Predictive Analytics, Scientists Are Getting Smarter About Outbreaks," 8 Nov. 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'microorganism.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of microorganism

1880, in the meaning defined above

History and Etymology for microorganism

International Scientific Vocabulary

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Statistics for microorganism

Last Updated

6 Apr 2019

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Time Traveler for microorganism

The first known use of microorganism was in 1880

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English Language Learners Definition of microorganism

biology : an extremely small living thing that can only be seen with a microscope


mi·​cro·​or·​gan·​ism | \ ˌmī-krō-ˈȯr-gə-ˌni-zəm How to pronounce microorganism (audio) \

Kids Definition of microorganism

: a living thing (as a bacterium) that can only be seen with a microscope


mi·​cro·​or·​gan·​ism | \ -ˈȯr-gə-ˌniz-əm How to pronounce microorganism (audio) \

Medical Definition of microorganism

: an organism of microscopic or ultramicroscopic size

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More from Merriam-Webster on microorganism

Spanish Central: Translation of microorganism

Nglish: Translation of microorganism for Spanish Speakers

Britannica.com: Encyclopedia article about microorganism

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What made you want to look up microorganism? Please tell us where you read or heard it (including the quote, if possible).


an enemy or opponent

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