\Cir"rus\, n.; pl. {Cirri}. [L., lock, curl, ringlet.]
[Also written {cirrhus}.]
1. (Bot.) A tendril or clasper.
2. (Zo["o]l.)
   (a) A soft tactile appendage of the mantle of many
       Mollusca, and of the parapodia of Annelida. Those near
       the head of annelids are Tentacular cirri; those of
       the last segment are caudal cirri.
   (b) The jointed, leglike organs of Cirripedia. See
       {Annelida}, and {Polych[ae]ta}.
Note: In some of the inferior animals the cirri aid in
      locomotion; in others they are used in feeding; in the
      Annelida they are mostly organs of touch. Some cirri
      are branchial in function.
3. (Zo["o]l.) The external male organ of trematodes and some
   other worms, and of certain Mollusca.
4. (Meteor.) See under {Cloud}.