mi·cro·or·gan·ism | \-ˈȯr-gə-ˌni-zəm \

Definition of microorganism 

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

Examples of microorganism in a Sentence

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In Castine Harbor, Castine Kayak Adventures runs paddle trips on weekends for stargazing and spotting glow-in-the-dark aquatic microorganisms. Megan Michelson, Outside Online, "These Are the Best Stargazing Spots in North America," 13 July 2018 There is also the risk, however rare, of Acanthamoeba Keratitis (or AK), a type of eye infection caused by a microorganism found in some tap water and swimming pools. Katie Heaney, The Cut, "Are My Contacts Going to Make Me Go Blind?," 11 July 2018 Indeed, there appear to be at least as many microorganism cells in the body as human cells. Jonathan Saltzman, BostonGlobe.com, "Startup aims to make allies of human gut’s microbes," 19 June 2018 This craft would carry instruments capable of identifying living microorganisms. David Grossman, Popular Mechanics, "New Evidence Suggests Possible Life on Venus," 3 Apr. 2018 Then Gehrig said Spaniak suggested studying the impact of weightlessness on Hydra, an immortal microorganism. Steve Sadin, chicagotribune.com, "North Shore students look to send their experiment to space," 2 July 2018 Studying these sponges, scientists have identified about 19,000 microorganisms that live in these sponges. Anne Geggis, Sun-Sentinel.com, "Sea sponges may hold key to fighting killer infections," 22 June 2018 In the late 1800s, the German-Austrian pediatrician Theodor Escherich gathered scientific evidence that microorganisms are part of the normal human system. Jonathan Saltzman, BostonGlobe.com, "Startup aims to make allies of human gut’s microbes," 19 June 2018 The algae bloom is filled with glowing phytoplankton that lights up when the microorganisms tumble down the face of waves at and near the shore. Gary Robbins, latimes.com, "Nighttime surf glowing with aqua-colored light dazzles San Diego beach," 9 May 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

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7 Sep 2018

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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 \

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 \

Medical Definition of microorganism 

: an organism of microscopic or ultramicroscopic size

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Spanish Central: Translation of microorganism

Nglish: Translation of microorganism for Spanish Speakers

Britannica.com: Encyclopedia article about microorganism

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