Merriam-Webster Collegiate Dictionary - amoeba

 also ameba  noun  (plural -bas or ~e)  Etymology: New Latin, genus name, from Greek amoibe change, from ameibein to change — more at migrate  Date: 1855 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