1 (pl. cirri) In certain ciliate Protozoa, an organelle, formed by the fusion of a group of cilia, which usually functions in locomotion.
2 In many invertebrates, a slender bodily appendage, often resembling a tentacle. In Polychaeta it bears cilia.
3 In some flatworms and trematodes, an eversible copulatory organ.
4 In some fishes (e.g. Creediidae) a tuft of skin on the jaw.
5 See Cirripedia.