||Cil"i*a (?), n. pl. Cilium, the sing., is rarely used. [L. cilium eyelid.] 1. (Anat.) The eyelashes.

2. (Biol.) Small, generally microscopic, vibrating appendages lining certain organs, as the air passages of the higher animals, and in the lower animals often covering also the whole or a part of the exterior. They are also found on some vegetable organisms. In the Infusoria, and many larval forms, they are locomotive organs.

3. (Bot.) Hairlike processes, commonly marginal and forming a fringe like the eyelash.

4. (Zoöl.) Small, vibratory, swimming organs, somewhat resembling true cilia, as those of Ctenophora.