any flagellate protozoan that is traditionally of the protozoan class Zoomastigophorea (sometimes called Zooflagellata), although recent classifications of this group have questioned the taxonomic usefulness of the term because some zooflagellates have been found to have photosynthetic capabilities and some phytoflagellates heterotrophic capabilities.

Zooflagellates assimilate organic material by osmotrophy (absorption through the plasma membrane) or phagotrophy (engulfing prey in food vacuoles). The zooflagellate's flexible pellicle (envelope) is sufficiently thin in certain genera to permit pseudopodal projections. Zooflagellates exhibit a considerable variation in form, and they may be free-living, symbiotic, commensal, or parasitic in humans and other animals and in certain plants. For additional information about zooflagellates, see choanoflagellate; Holomastigotoides; hypermastigote; protomonad; trichomonad.