The term 'Primitive Creature' can be summarized by the crossword solution 'AMOEBA', which is a single-celled organism that has existed for millions of years. Amoebas are classified as protists, and they are able to move and change shape by extending and retracting their pseudopods. They feed on bacteria and other small organisms, and reproduce by splitting in two. Amoebas are considered primitive creatures because they have remained relatively unchanged over time.