1. Any of various protozoans with whip-like appendages of the subclass Zoomastigina, lacking plantlike characteristics: Zooflagellates are protozoa possessing moveable threadlike or lash-like structures, or "flagellum", and specifically those protozoa having "flagella" (plural of "flagellum") or long, whip-like "tails" of certain cells in both the plant and animal kingdoms, which undulates with a regular pattern. They are used primarily for locomotion and also for other purposes, such as attracting food particles or moving substances through a "mouth" cavity.
2. Etymology: from Latin meaning "whip".