any organism, such as a bacterium, protozoan, or virus, of microscopic size
WordReference Random House Learner's Dictionary of American English © 2025
mi•cro•or•gan•ism /ˌmaɪkroʊˈɔrgəˌnɪzəm/USA pronunciation
n. [countable]
WordReference Random House Unabridged Dictionary of American English © 2025- Microbiologyany organism too small to be viewed by the unaided eye, as bacteria or some fungi and algae.
mi•cro•or•gan•ism
(mī′krō ôr′gə niz′əm),USA pronunciation n.
mi•cro•or•gan•ic
(mī′krō ôr gan′ik),USA pronunciation mi′cro•or′gan•is′mal, adj.
- Microbiologyany organism too small to be viewed by the unaided eye, as bacteria, protozoa, and some fungi and algae.
- 1875–80; micro- + organism
Collins Concise English Dictionary © HarperCollins Publishers::
'microorganism' also found in these entries (note: many are not synonyms or translations):
Rocky Mountain spotted fever
- agent
- auxotroph
- bug
- contagious
- cross-resistance
- cytopathogenic
- defense mechanism
- endotoxin
- exotoxin
- germ
- hematophyte
- isolate
- micro
- microbe
- microparasite
- mycoplasma
- nystatin
- opportunistic
- opsonify
- pathogen
- phagocytosis
- polyvalent
- prochloron
- prototroph
- pure culture
- rickettsia
- rod
- scrub typhus
- superbug
- superinfection
- syphilis
- trench fever
- trichome
- tsutsugamushi disease
- vector
- virulence
- virulent