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

The microorganisms living in the microbial mat feed on decaying organic material. —David Bressan, Forbes.com, 30 Aug. 2025

Skin odors, genetics, and microbiota (various bacteria, fungi, and other microorganisms) on the skin also may play a role. —Sherri Gordon, Health, 28 Aug. 2025

If a banana peel is buried in the soil, microorganisms will work to break it down. —Lauren David, Southern Living, 21 Aug. 2025

These beans are known to ferment naturally, so there’s little scope to know about the microorganisms involved in the process. —Atharva Gosavi, Interesting Engineering, 20 Aug. 2025

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