from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. Any of a large group of single-celled, usually microscopic, eukaryotic organisms, such as amoebas, ciliates, flagellates, and sporozoans.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. Any of the diverse group of eukaryotes, of the phylum Protozoa, 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.
  • adj. Of, pertaining to, or characteristic of a protozoan.

from the GNU version of the Collaborative International Dictionary of English

  • adj. Of or pertaining to the protozoa.

from The Century Dictionary and Cyclopedia

  • First, lowest, simplest, or most primitive, as an animal; of or pertaining to the Protozoa.
  • n. A member of the Protozoa; a protozoön.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • n. any of diverse minute acellular or unicellular organisms usually nonphotosynthetic
  • adj. of or relating to the Protozoa


from The American Heritage® Dictionary of the English Language, 4th Edition

From New Latin Protozōa, former subkingdom name : proto- + -zōa, pl. of -zōon, -zoon.


  • Well, I suppose a protozoan could be a protagonist, added Charlotte.

    Freaked Out

  • While the structure of this sentence is strictly accurate it has led several readers to point out that neither affliction results from a virus – babesia is a protozoan and fog fever is caused by the toxin 3-methylindole.

    Corrections and clarifications

  • You don't need to travel to a tropical location to contract a protozoan infection.

    Intestinal Parasites May Be Causing Your Energy Slump

  • Another protozoan that's achieved notoriety in the U.S. is Cryptosporidium parvum, which contaminated Milwaukee's water supply in the 1990's, causing the largest epidemic of diarrhea in U.S. history, infecting about 400,000 people and causing over one hundred deaths.

    Intestinal Parasites May Be Causing Your Energy Slump

  • For instance, the malaria protozoan Plasmodium falciparum infects humans, causing the malarial symptoms that everyone knows about, but it affects the mosquitoes, too.


  • A protozoan has the potential of evolving into a human being.

    Archive 2009-06-01

  • Pick any eukaryotic species (say, the ciliated protozoan Tetrahymena thermophila) — one cannot be certain that a member of that species shares common ancestry, from a discrete cell, with a member of any other eukaryotic species (say, Drosophila melanogaster).

    A Disclaimer for Behe?

  • In a pioneering experiment, they demonstrated that telomere DNA from one organism, a unicellular ciliated protozoan called Tetrahymena thermophila, would protect and stabilise chromosomes in an entirely different organism, yeast.

    The 2009 Nobel Prize in Physiology or Medicine - Presentation Speech

  • January 18th, 2010 at 6: 47 pm pluege says: this statement ought to really raise chavez in the eyes of other vermin scum like limbaugh and beck. the indecency of these cretinous sub-humanoid flotsam of protozoan malformation is startling no matter how common their inhuman malfeasance gets.

    Think Progress » Chavez Attacks U.S. Efforts In Haiti: ‘They Are Occupying Haiti Undercover’

  • There remains virtually no river in the U.S. where drinking its water doesn't risk catching Giardia lamblia or some other nasty flagellated protozoan parasite, but here the luminous water is eminently potable.

    Richard Bangs: Bosnia & Herzegovina, That Unreal Place


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