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

Live yogurt contains nutrients and beneficial microorganisms that boost plant growth and health. —Lauren Landers, The Spruce, 8 June 2026

Clippings are broken down by microorganisms, like bacteria and fungi, that feed the soil microbiome and help cycle nutrients efficiently into the soil. —Rachel Silva, Martha Stewart, 7 June 2026

Optical systems are blazing fast but require a direct line of sight and fail in murky water or when the buildup of microorganisms degrades the lenses. —Omar Kardoudi june 06, New Atlas, 6 June 2026

Probiotics are live microorganisms that can help improve or restore your gut microbiota. —Emmanuella Ogbonna, Health, 5 June 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