protozoan

American  

[proh-tuh-zoh-uhn] / ˌproʊ təˈzoʊ ən /

noun

protozoans, plural protozoa plural

1. 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 means of motility, as by pseudopods, flagella, or cilia.

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adjective

1. of, relating to, or characteristic of a protozoan.

protozoan British  

/ ˌprəʊtəˈzəʊən /

noun

1. Also called: protozoon.  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

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adjective

1. of or relating to protozoans

protozoan Scientific  

/ prō′tə-zō′ən /

protozoans plural

1. Any of a large group of one-celled organisms (called protists) that live in water or as parasites. Many protozoans move about by means of appendages known as cilia or flagella. Protozoans include the amoebas, flagellates, foraminiferans, and ciliates. Their traditional classification as the subkingdom Protozoa is still used for convenience, but it is now known that protozoans represent several evolutionarily distinct groups.

2. See more at protist

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Etymology

Origin of protozoan

First recorded in 1860–65; Protozo(a) + -an

Example Sentences

Giardia duodenalis is a microscopic protozoan parasite known for causing outbreaks of severe diarrhea.

From Science Daily • Dec. 21, 2025

It’s not yet clear, however, exactly how the Amazonian variant wards off the protozoan invader.

From Science Magazine • Mar. 7, 2023

It's a protozoan, similar to the malaria parasite.

From Salon • Nov. 1, 2022

One common protozoan disease known to occur in birds, which evolved from feathered dinosaurs, as well as in people is called trichomoniasis, caused by a parasitic protozoan.

From Reuters • Oct. 1, 2022

They are outsiders, in to help with the business: fully formed, perfect spirochetes that have attached themselves at regularly spaced intervals all over the surface of the protozoan.

From "The Lives of a Cell" by Lewis Thomas