protozoan

American  

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

noun

plural

protozoans,

plural

protozoa

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 /

plural

protozoans

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

A research team placed Halteria ciliates—a type of protozoan with hairlike organelles found in freshwater worldwide—in a petri dish with only chloroviruses, which infect green algae.

From Science Magazine • Jan. 11, 2023

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

Though the idea of a mind-altering protozoan transmitted via cats is alarming, it is not necessarily harmful: roughly 30 percent of the human population is infected with the T gondii parasite.

From Salon • Apr. 19, 2022

Scientists in Czechoslovakia are experimenting with protozoa against webworms and other insect pests, and in the United States a protozoan parasite has been found to reduce the egg- laying potential of the corn borer.

From "Silent Spring" by Rachel Carson