The Collaborative International Dictionary of English v.0.48:

Birch \Birch\ (b[~e]rch), n.; pl. Birches (-[e^]z). [OE.
   birche, birk, AS. birce, beorc; akin to Icel. bj["o]rk, Sw.
   bj["o]rk, Dan. birk, D. berk, OHG. piricha, MHG. birche,
   birke, G. birke, Russ. bereza, Pol. brzoza, Serv. breza, Skr.
   bh[=u]rja. [root]254. Cf. 1st Birk.]
   1. A tree of several species, constituting the genus
      Betula; as, the white or common birch (Betula alba)
      (also called silver birch and lady birch); the dwarf birch
      (Betula glandulosa); the paper or canoe birch (Betula
      papyracea); the yellow birch (Betula lutea); the black
      or cherry birch (Betula lenta).
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   2. The wood or timber of the birch.
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   3. A birch twig or birch twigs, used for flogging.
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   Note: The twigs of the common European birch (B. alba), being
         tough and slender, were formerly much used for rods in
         schools. They were also made into brooms.
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               The threatening twigs of birch.    --Shak.
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   4. A birch-bark canoe.
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   Birch of Jamaica, a species (Bursera gummifera) of
      turpentine tree.

   Birch partridge. (Zool.) See Ruffed grouse.

   Birch wine, wine made of the spring sap of the birch.

   Oil of birch.
      (a) An oil obtained from the bark of the common European
          birch (Betula alba), and used in the preparation of
          genuine (and sometimes of the imitation) Russia
          leather, to which it gives its peculiar odor.
      (b) An oil prepared from the black birch (Betula lenta),
          said to be identical with the oil of wintergreen, for
          which it is largely sold.
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The Collaborative International Dictionary of English v.0.48:

Birch \Birch\, v. t. [imp. & p. p. Birched (b[~e]rcht); p. pr.
   & vb. n. Birching.]
   To whip with a birch rod or twig; to flog.
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The Collaborative International Dictionary of English v.0.48:

Birch \Birch\, a.
   Of or pertaining to the birch; birchen.
   [1913 Webster]

WordNet (r) 3.0 (2006):

birch
    adj 1: consisting of or made of wood of the birch tree [syn:
           birch, birchen, birken]
    n 1: hard close-grained wood of any of various birch trees; used
         especially in furniture and interior finishes and plywood
    2: any betulaceous tree or shrub of the genus Betula having a
       thin peeling bark [syn: birch, birch tree]
    3: a switch consisting of a twig or a bundle of twigs from a
       birch tree; used to hit people as punishment; "my father
       never spared the birch" [syn: birch, birch rod]
    v 1: whip with a birch twig