Definition of "cilium"

(cytology) A short microscopic hairlike organelle projecting from a eukaryotic cell (such as a unicellular organism or one cell of a multicelled organism) which serve either for propulsion by causing currents in the surrounding fluid or as sensors.

(entomology) One of the fine hairs along an insect's wing.

(botany) Hairs or similar protrusions along the margin of an organ.  examples

(anatomy) An eyelash.  examples