Source : Webster's Revised Unabridged Dictionary (1913)

Barn \Barn\, n. [OE. bern, AS. berern, bern; bere barley + ern,
   [ae]rn, a close place. ?92. See {Barley}.]
   A covered building used chiefly for storing grain, hay, and
   other productions of a farm. In the United States a part of
   the barn is often used for stables.

   {Barn owl} (Zo["o]l.), an owl of Europe and America ({Aluco
      flammeus}, or {Strix flammea}), which frequents barns and
      other buildings.

   {Barn swallow} (Zo["o]l.), the common American swallow
      ({Hirundo horreorum}), which attaches its nest of mud to
      the beams and rafters of barns.

Source : WordNet®

barn swallow
     n : common swallow of North America and Europe that nests in
         barns etc. [syn: {chimney swallow}, {Hirundo rustica}]