protozoanPronunciation: /ˌprəʊtə(ʊ)ˈzəʊən/ ZoologyDefinition of protozoan noun a single-celled microscopic animal of a group of phyla of the kingdom Protista, such as an amoeba, flagellate, ciliate, or sporozoan. adjective relating to or denoting protozoans. Derivatives protozoal adjective protozoic adjective protozoonPronunciation: /-ˈzəʊɒn/ noun protozoan in other Oxford dictionaries Definition of protozoan in the US English dictionary