mastigote

Etymology
From.

Noun

 * 1) A single-celled microorganism that moves by means of an undulipodium, such as a flagellum, rather than using pseudopodia.

Usage notes

 * An organism may be a mastigote throughout its life cycle, or may spend part of its life as an amoeboid cell, and part of its life as a mastigote. The term is therefore not used for  classification in a taxonomic sense.