noun pl. amoebas -·bas or amoebae -·bae (-bē)

1. a one-celled, microscopic organism belonging to any of several families of rhizopods that move and feed using pseudopodia and reproduce by fission; esp., any of a genus (Amoeba) found in soil or water or a parasitic genus (Entamoeba) found in higher animals and humans
2. something indefinite in shape or perpetually changing, like an amoeba

Etymology: ModL < Gr amoibē, change < ameibein, to change