Cilium is a see also of undulipodium.

As nouns the difference between cilium and undulipodium

is that cilium is (cytology) a hairlike organelle projecting from a eukaryotic cell (such as a unicellular organism or one cell of a multicelled organism) these structures serve either for locomotion by moving or as sensors while undulipodium is an intracellular projection of a eukaryotic cell containing a microtubule array, used for locomotion or for propelling fluids.