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

Taylor’s research on didymo blooms in Colorado has led him to believe that the growth is triggered by a combination of environmental conditions and, potentially, infection by another microorganism. — Hannah Smith july 25, Idaho Statesman, 25 July 2026

Buildup can include microorganisms, algae, plants and invertebrates. — Julia Jacobo, ABC News, 25 July 2026

In parallel, researchers are studying marine microorganisms capable of growing in seawater and utilizing alternative feedstocks. — Jijo Malayil, Interesting Engineering, 24 July 2026

Further research is needed to identify the specific microorganisms and pathways that might be responsible for improved sleep. — Erica Sweeney, EverydayHealth.com, 24 July 2026

Word History

Etymology

International Scientific Vocabulary

First Known Use

1880, in the meaning defined above

Rhymes for microorganism

• activism
• albinism
• altruism
• aneurism
• animism
• aphorism
• atomism
• barbarism
• bolshevism
• botulism
• brahmanism
• calvinism

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