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

The adult resident is being treated for Naegleria fowleri, a rare and deadly microscopic amoeba that can cause primary amebic meningoencephalitis (PAM), according to the press release. —Caroline Zimmerman, Kansas City Star, 13 Aug. 2025

How both pathogens can enter the body during water activities: Why is it called a brain-eating amoeba? —Janet Loehrke, USA Today, 3 Aug. 2025

Because the amoeba is found in soil, the CDC also recommends avoiding stirring up the sediment at the bottom of lakes, ponds and rivers. —Melissa Rudy, FOXNews.com, 25 July 2025

Last month, a 71-year-old Texas woman died from the brain-eating amoeba after flushing her sinuses with tap water, health officials said. —Muri Assunção, New York Daily News, 23 July 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