microorganism

[mahy-kroh-awr-guh-niz-uh m] /ˌmaɪ kroʊˈɔr gəˌnɪz əm/
noun
1.
any organism too small to be viewed by the unaided eye, as bacteria, protozoa, and some fungi and algae.
Origin
1875-80; micro- + organism
Related forms
microorganic
[mahy-kroh-awr-gan-ik] /ˌmaɪ kroʊ ɔrˈgæn ɪk/ (Show IPA), microorganismal, adjective
Examples from the web for microorganism
  • He had identified the microorganism that causes a form of pneumonia in humans.
  • The genomics gold rush revolves around genes that have been isolated and purified outside an animal, plant or microorganism.
  • The antibody and other parts of the immune system destroy and eliminate the invading microorganism.
  • Yeast is the microorganism that is responsible for fermentation in beer.
British Dictionary definitions for microorganism

microorganism

/ˌmaɪkrəʊˈɔːɡəˌnɪzəm/
noun
1.
any organism, such as a bacterium, protozoan, or virus, of microscopic size
microorganism in Medicine

microorganism mi·cro·or·gan·ism (mī'krō-ôr'gə-nĭz'əm)
n.
An organism of microscopic or submicroscopic size, especially a bacterium or protozoan.

microorganism in Science
microorganism
  (mī'krō-ôr'gə-nĭz'əm)   
An organism that can be seen only with the aid of a microscope and that typically consists of only a single cell. Microorganisms include bacteria, protozoans, and certain algae and fungi. See Note at germ.