Cilium

Definition
noun, plural: cilia
(biology)
Microscopic, hair-like projection on the surfaces of some cells and of certain organisms.
(botany)
Any of the hair forming a fringe along the margin or edge of a plant structure, e.g. of a leaf.
(anatomy)
The eyelash.
Supplement
Cilia are generally of two kinds: motile cilia (for locomotion) and non-motile cilia (for sensory). Example of tissue cells with cilia are the epithelia lining the lungs that sweep away fluids or particles. Examples of organisms that have cilia are protozoans that use them for movement.
Word origin: NL, pl. of cilium eyelash, L: upper eyelid.
Related phrases: immotile cilia syndrome.
Compare: flagellum.