Dictionary
mi•cro•or•gan•ism
Pronunciation: (mī"krō-ôr'gu-niz"um), [key]—
n.
any organism too small to be viewed by the unaided eye, as bacteria, protozoa, and some fungi and algae.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.