Source : Webster's Revised Unabridged Dictionary (1913)

Barnacle \Bar"na*cle\, n. [See {Bernicle}.]
   A bernicle goose.

Barnacle \Bar"na*cle\, n. [OE. bernak, bernacle; cf. OF. bernac,
   and Prov. F. (Berri) berniques, spectacles.]
   1. pl. (Far.) An instrument for pinching a horse's nose, and
      thus restraining him.

   Note: [Formerly used in the sing.]

               The barnacles . . . give pain almost equal to
               that of the switch.                --Youatt.

   2. pl. Spectacles; -- so called from their resemblance to the
      barnacles used by farriers. [Cant, Eng.] --Dickens.

Barnacle \Bar"na*cle\, n. [Prob. from E. barnacle a kind of
   goose, which was popularly supposed to grow from this
   shellfish; but perh. from LL. bernacula for pernacula, dim.
   of perna ham, sea mussel; cf. Gr. ? ham Cf. F. bernacle,
   barnacle, E. barnacle a goose; and Ir. bairneach, barneach,
   limpet.] (Zo["o]l.)
   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} (Zo["o]l.), the orange filefish.

   {Barnacle scale} (Zo["o]l.), a bark louse ({Ceroplastes
      cirripediformis}) of the orange and quince trees in
      Florida. The female scale curiously resembles a sessile
      barnacle in form.

Source : WordNet®

barnacle
     n 1: marine crustaceans with feathery food-catching appendages;
          free-swimming as larvae; as adults form a hard shell and
          live attached to submerged surfaces [syn: {cerriped}, {cerripede}]
     2: European goose smaller than the brant; breeds in the far
        north [syn: {barnacle goose}, {Branta leucopsis}]