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[proh-tuh-zoh-uh n]Biology
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noun, plural pro·to·zo·ans, (especially collectively) pro·to·zo·a [proh-tuh-zoh-uh] /ˌproʊ təˈzoʊ ə/.
  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.
  1. of, relating to, or characteristic of a protozoan.

Origin of protozoan

First recorded in 1860–65; Protozo(a) + -an
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for protozoan

Historical Examples

  • Inside this snail's gut there is a protozoan that lives off the snail's ingested food.

    Planet of the Damned

    Harry Harrison

  • A species of Vorticella was probably the first Protozoan that was ever observed.

    Insects and Diseases

    Rennie W. Doane

  • Protozoan parasites in relation to the host and to host ecology.

  • Description of the protozoan parasites recognized in this study.

  • The Protozoan swims by the vibration of these cilia in the water.

British Dictionary definitions for protozoan


noun plural -zoa (-ˈzəʊə) or -zoans
  1. Also called: protozoon (ˌprəʊtəˈzəʊɒn) plural -zoa 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
adjective Also: protozoic
  1. of or relating to protozoans

Word Origin

C19: via New Latin from Greek proto- + zoion animal
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

protozoan in Medicine


n. pl. pro•to•zo•a (-zōə)
  1. Any of a group of single-celled, usually microscopic, eukaryotic organisms, such as amoebas, ciliates, flagellates, and sporozoans.
Related formspro′to•zoan null null adj.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

protozoan in Science


Plural protozoans protozoa
  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. See more at protist.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.