Real Dictionary

protozoan
Protozoa are very small organisms which often live inside larger animals.

protozoan in American English
any of a subkingdom (Protozoa) of microscopic animals made up of a single cell or a group of more or less identical cells and living in water or as parasites, including ciliates, flagellates, rhizopods, and sporozoans

protozoan in American Englishesp collectively
adjective: of, pertaining to, or characteristic of a protozoan
noun: any of a diverse group of eukaryotes, of the kingdom Protista, that are primarily unicellular, existing singly or aggregating into colonies, are usually nonphotosynthetic, and are often classified further into phyla according to their capacity for and mea

protozoan in British English
adjective: of or relating to protozoans
noun: any of various minute unicellular organisms formerly regarded as invertebrates of the phylum Protozoa but now usually classified in certain phyla of protoctists. Protozoans include flagellates, ciliates, sporozoans, amoebas, and foraminifers