amoeba

noun

amoe·​ba ə-ˈmē-bə 

variants or less commonly ameba

plural amoebas or amoebae also amebas or amebae ə-ˈmē-(ˌ)bē 

: any of a large genus (Amoeba) of naked rhizopod protozoans with lobed and never anastomosing pseudopodia, without permanent organelles or supporting structures, and of wide distribution in fresh and salt water and moist terrestrial environments

broadly : a naked rhizopod or other amoeboid protozoan

amoebic adjective

or less commonly amebic

ə-ˈmē-bik

Illustration of amoeba

• 1 pseudopodium
• 2 nucleus
• 3 contractile vacuole
• 4 food vacuole

Examples of amoeba in a Sentence

Recent Examples on the Web

Perhaps the scariest—but also the rarest, with fewer than 10 cases in the U.S. annually—is Naegleria fowleri (N. fowleri), an amoeba that can cause a fatal brain infection. —Julia Ries, Health, 17 June 2025

Treatment of brain-eating amoebas When a patient has been diagnosed with a brain-eating amoeba, treatment usually includes a variety of antifungal medications, as well as antibiotics like rifampin and azithromycin, according to Lundstrom. —Melissa Rudy, FOXNews.com, 6 June 2025

Brain-eating amoeba is most commonly found in warm fresh waters such as lakes, rivers and hot springs. —Vanessa Etienne, People.com, 3 June 2025

The patient was treated for a potential infection of primary amebic meningoencephalitis (PAM), a rare, deadly brain infection caused by Naegleria fowleri, also known as the brain-eating amoeba. —Melissa Rudy, FOXNews.com, 6 June 2025

Word History

Etymology

New Latin, genus name, from Greek amoibē change, from ameibein to change — more at migrate

First Known Use

1822, in the meaning defined above

Rhymes for amoeba

• ameba
• ceiba
• iba
• rebbe
• copaiba
• entamoeba

Kids Definition

amoeba

noun

amoe·​ba

variants also ameba

ə-ˈmē-bə

plural amoebas or amoebae -(ˌ)bē 

: any of a large genus of protozoans that have no permanent cell organs or structures, that change shape to form temporary lobes for moving and taking in food, and that are widespread in fresh and salt water and in moist soils

amoebic

-bik 

adjective

Medical Definition

amoeba

noun

amoe·​ba

ə-ˈmē-bə

1

capitalized : a large genus of naked rhizopod protozoans that have lobed and never anastomosing pseudopodia and are widely distributed in fresh and salt water and moist terrestrial environments

2

also ameba plural amoebas or amoebae -(ˌ)bē  also amebas or amebae : a protozoan of the genus Amoeba

broadly : an amoeboid protozoan (as a naked rhizopod)

amebic adjective

or amoebic

-bik