The Collaborative International Dictionary of English v.0.48:

Mahogany \Ma*hog"a*ny\, Mahogany tree \Ma*hog"a*ny tree`\, n.
   [From the South American name.]
   1. (Bot.) A large tree of the genus Swietenia (Swietenia
      Mahogoni), found in tropical America.
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   Note: Several other trees, with wood more or less like
         mahogany, are called by this name; as, African mahogany
         (Khaya Senegalensis), Australian mahogany
         (Eucalyptus marginatus), Bastard mahogany (Batonia
         apetala of the West Indies), Indian mahogany (Cedrela
         Toona of Bengal, and trees of the genera Soymida and
         Chukrassia), Madeira mahogany (Persea Indica),
         Mountain mahogany, the black or cherry birch (Betula
         lenta), also the several species of Cercocarpus of
         California and the Rocky Mountains.
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   2. The wood of the Swietenia Mahogoni. It is of a reddish
      brown color, beautifully veined, very hard, and
      susceptible of a fine polish. It is used in the
      manufacture of furniture.
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   3. A table made of mahogany wood. [Colloq.]
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   To be under the mahogany, to be so drunk as to have fallen
      under the table. [Eng.]

   To put one's legs under some one's mahogany, to dine with
      him. [Slang]
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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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WordNet (r) 3.0 (2006):

Betula lenta
    n 1: common birch of the eastern United States having spicy
         brown bark yielding a volatile oil and hard dark wood used
         for furniture [syn: sweet birch, cherry birch, black
         birch, Betula lenta]