An amoeba (also ameba, amoeba amœba or) amoeboid is a type of cell or organism which has the ability to alter its, shape primarily by extending and retracting. pseudopodsicrobiologists often use the terms amoeboid and amoebae interchangeably for any organism that exhibits amoeboid movement. In older classification systems, most amoebae were placed in the class or subphylum Sarcodina, a grouping of single-celled organisms that possess pseudopods or move by protoplasmic flow.