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

Synthetic fertilizers are designed for rapid nutrient delivery and may promote quick growth; however, the elevated salt content and high NPK levels in synthetic fertilizers can harm soil health, disrupt beneficial microorganisms, and cause nutrient imbalances. —Rita Perwich, San Diego Union-Tribune, 7 Mar. 2026

Overuse can also harm the environment and disrupt beneficial microorganisms. —Caroline Lubinsky, Martha Stewart, 5 Mar. 2026

Scientists have long known that vast colonies of bacteria, viruses and other microorganisms—a population collectively called the microbiome—live on and inside the human body. —K. R. Callaway, Scientific American, 26 Feb. 2026

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