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

An 8-year-old girl in Louisiana died after she was infected with a rare brain-eating amoeba, leaving her family devastated. — Julia Gomez, USA Today, 25 Aug. 2026

The amoeba can lead to a fatal infection known as primary amoebic meningoencephalitis when water carrying the amoeba travels up the nose and into the brain. — Jack Brook, Fortune, 25 Aug. 2026

An 8-year-old has died after contracting a rare brain-eating amoeba believed to have been encountered while swimming in a lake near her home, her family and health officials said. — Diego Mendoza, CNN Money, 24 Aug. 2026

Lillian Smart, an 8-year-old girl who health officials believe contracted a brain-eating amoeba while swimming in a northern Louisiana lake, died Saturday at a Ruston hospital from an infection linked to the pathogen. — Brittany Miller, FOXNews.com, 24 Aug. 2026

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