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.
Probiotic Foods Probiotics are beneficial microorganisms, including bacteria and yeasts, that help increase good bacteria in the gut while reducing harmful ones. Jamie Johnson, Verywell Health, 22 May 2025 Gut Benefits of Probiotics Your GI tract is full of microorganisms, some good and some bad. Health, 19 May 2025 But some microorganisms, known as extremophiles, show impressive resilience in inhospitable environments, whether that's the vacuum of space, hydrothermal vents on the slopes of undersea volcanoes, or even NASA clean rooms. Stefanie Waldek, Space.com, 18 May 2025 Yet, even after the French microbiologist Louis Pasteur patented the technology of pasteurization, or heating liquids to kill microorganisms, in 1865, Americans largely continued to consume raw milk for several more decades. Made By History, Time, 29 Apr. 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 6 Jun. 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

More from Merriam-Webster on microorganism

Last Updated: - Updated example sentences
Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!