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

This device emits radiation that damages the cells of microorganisms like bacteria and mold—keeping the coil and interior components clean. —Matt Fuchs, Time, 12 June 2025

What Molasses Does in the Garden Molasses’ power in the garden lies in its ability to feed beneficial microorganisms in the soil that play a vital role in plant health. —Leanne Potts, Better Homes & Gardens, 11 June 2025

Rich in microorganisms and volatile organic compounds, the woodland environment strengthens the immune system, enhances brain function, and lifts our mood. —Emese MacZko, Forbes.com, 10 June 2025

In one small study, adults with obesity who drank black tea kombucha for eight weeks had an improved balance of beneficial gut microorganisms compared to normal-weight adults.5 Immunity and the gut microbiome: Kombucha may enhance immune system health. —Melissa Nieves, Verywell Health, 9 June 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