Pronunciation (UK) IPA (key): /ˈɔː.ɡən.ɪ.zəm/ (US) IPA (key): /ˈɔr.ɡən.ɪ.zəm/ Audio (US)(file) Noun Singular organism Plural organisms (countable) (biology) An organism is any living thing, such as an animal, a plant, or a bacterium. The Earth is full of many different kinds of organisms.Wikiwand - on Seamless Wikipedia browsing. On steroids.Remove ads