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

One reason for this is that peppermint oil has known antimicrobial properties and can destroy harmful microorganisms. — Bestreviews, Chicago Tribune, 13 Aug. 2026

Microbes, also called microorganisms, are living agents that are too small to be seen with the unaided eye. — Encyclopedia Britannica, 11 Aug. 2026

These products last on shelves because they are not exposed to microorganisms in water or soil. — ABC News, 10 Aug. 2026

Your gut contains trillions of microorganisms that help with digestion, nutrient absorption, and immune function. — Sarah Jividen, Verywell Health, 4 Aug. 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