The Collaborative International Dictionary of English v.0.48:

Barley \Bar"ley\, n. [OE. barli, barlich, AS. b[ae]rlic; bere
   barley + l[imac]c (which is prob. the same as E. like, adj.,
   or perh. a form of AS. le[=a]c leek). AS. bere is akin to
   Icel, barr barley, Goth. barizeins made of barley, L. far
   spelt; cf. W. barlys barley, bara bread. ?92. Cf. Farina,
   6th Bear.] (Bot.)
   A valuable grain, of the family of grasses, genus Hordeum,
   used for food, and for making malt, from which are prepared
   beer, ale, and whisky.
   [1913 Webster]

   Barley bird (Zool.), the siskin.

   Barley sugar, sugar boiled till it is brittle (formerly
      with a decoction of barley) and candied.

   Barley water, a decoction of barley, used in medicine, as a
      nutritive and demulcent.
      [1913 Webster] Barleybrake

WordNet (r) 3.0 (2006):

barley
    n 1: a grain of barley [syn: barley, barleycorn]
    2: cultivated since prehistoric times; grown for forage and
       grain