- any organism too small to be viewed by the unaided eye, as bacteria, protozoa, and some fungi and algae.
Origin of microorganism
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
Examples from the Web for micro-organism
A micro-organism is a parasite when it can live in animal tissues.Essays In Pastoral Medicine
The micro-organism is found in the secretions from the mouth, throat, or nose, and in particles of detached membrane.Health on the Farm
H. F. Harris
Altogether there are many obscure points about this micro-organism, which is apt to assume a puzzling variety of forms.
There are many kinds of fermentation, each with its own special form of minute plant life or micro-organism.A Practical Physiology
Albert F. Blaisdell
The micro-organism of small-pox and that of cancer (the existence of which is assumed) have not yet been isolated.Beacon Lights of History, Volume XIV
- any organism, such as a bacterium, protozoan, or virus, of microscopic size
Word Origin and History for micro-organism
Online Etymology Dictionary, © 2010 Douglas Harper
- An organism of microscopic or submicroscopic size, especially a bacterium or protozoan.
- 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.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.