cilium

Short definition from Wiktionary

Noun

1. 1
   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.
2. 2
   One of the fine hairs along an insect's wing.
3. 3
   One of the hairs or similar protrusions along the margin of an organ.
4. 4
   An eyelash.