What does "microorganism" mean?

An organism that is too small to be seen by the unaided eye; especially, a single-celled organism, such as a bacterium.

What is a synonym for "microorganism"?

Common synonyms include: microbe, adenovirus, aerobe, aerobic bacteria, aerobic organism, amebic.

Pronounced //ˌmaɪ.kɹəʊˈɔː.ɡəˌnɪz.m̩//.

//ˌmaɪ.kɹəʊˈɔː.ɡəˌnɪz.m̩// noun

noun ·Moderate ·College level

Noun

1
An organism that is too small to be seen by the unaided eye; especially, a single-celled organism, such as a bacterium.
"The cud is then reswallowed and further digested by specialized microorganisms that live in the rumen."
2
any organism of microscopic size wordnet

"Tom succeeded in culturing the new microorganism."

From micro- + organism.

Data sourced from Wiktionary, WordNet, CMU, and other open linguistic databases. Updated March 2026.