noun
pl. protozoans or protozoa 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
Origin:
< ModL Protozoa, name of the phylum (see proto- & -zoa) + -an