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

Tumbling towels in an automatic dryer will help sanitize towels and kill microorganisms. — Mary Marlowe Leverette, Southern Living, 9 July 2026

Electric blue waves were also spotted in 2016, but the microorganisms that cause the light are more frequently seen in the sound. — Eva Flowe july 8, Charlotte Observer, 8 July 2026

Green cabbage tends to be more common for fermenting, a process by which microorganisms (bacteria, yeast, or fungi) break down sugars and starches in food, producing acids, gases, or alcohol as byproducts. — Lauren Panoff, Verywell Health, 8 July 2026

Water from washing off rice contains nutrients and microorganisms that boost plant growth and soil fertility. — Leanne Potts, Better Homes & Gardens, 7 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