microorganism

noun

mi·​cro·​or·​gan·​ism ˌmī-krō-ˈȯr-gə-ˌni-zəm 

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

Examples of microorganism in a Sentence

Recent Examples on the Web

Glyphosate inhibits protein synthesis in plants and microorganisms, leading to their death. —Michal Ruprecht, CNN Money, 24 Feb. 2026

Key Takeaways Probiotic drinks such as kefir, kombucha, and yogurt drinks contain beneficial live microorganisms, including bacteria and yeasts. —Lana Barhum, Verywell Health, 23 Feb. 2026

Soluble fiber can also boost your gut microbiome—the vast population of bacteria and other microorganisms that live in your digestive tract and mediate multiple aspects of your health—in a big way. —Carolyn L. Todd, SELF, 23 Feb. 2026

But rather than relying on microorganisms, Astroforge has been working on a process that involves lasers and magnets to extract minerals from asteroids. —Julian Dossett, Space.com, 20 Feb. 2026

Word History

Etymology

International Scientific Vocabulary

First Known Use

1880, in the meaning defined above

Rhymes for microorganism

• absolutism
• adventurism
• aestheticism
• africanism
• agnosticism
• alcoholism
• anabolism
• anachronism
• anglicanism
• antagonism
• arianism
• asceticism

Kids Definition

microorganism

noun

mi·​cro·​or·​gan·​ism ˌmī-krō-ˈȯr-gə-ˌniz-əm 

: 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 

: an organism of microscopic or ultramicroscopic size