Bar·na·cle n.  Zool. Any cirriped crustacean adhering to rocks, floating timber, ships, etc., esp. (a) the sessile species (genus Balanus and allies), and (b) the stalked or goose barnacles (genus Lepas and allies). See Cirripedia, and Goose barnacle.
 Barnacle eater Zool., the orange filefish.
 Barnacle scale Zool., a bark louse (Ceroplastes cirripediformis) of the orange and quince trees in Florida. The female scale curiously resembles a sessile barnacle in form.