cilia definition
A cilium (plural cilia) is an organelle found in eukaryotic cells. Cilia are slender protuberances that project from the much larger cell body. There are two types of cilia:1  motile cilia, which beat against fluid outside the cell. 2  non-motile, or primary cilia, which typically serve as sensory organelles. cilium (plural cilia) is an organelle found in eukaryotic cells. Cilia are slender protuberances that project from the much larger cell body. There are two types of cilia: