The Collaborative International Dictionary of English v.0.48:

Song \Song\ (s[o^]ng; 115), n. [AS. song, sang, fr. singan to
   sing; akin to D. zang, G. sang, Icel. s["o]ngr, Goth. saggws.
   See Sing.]
   1. That which is sung or uttered with musical modulations of
      the voice, whether of a human being or of a bird, insect,
      etc. "That most ethereal of all sounds, the song of
      crickets." --Hawthorne.
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   2. A lyrical poem adapted to vocal music; a ballad.
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   3. More generally, any poetical strain; a poem.
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            The bard that first adorned our native tongue
            Tuned to his British lyre this ancient song.
                                                  --Dryden.
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   4. Poetical composition; poetry; verse.
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            This subject for heroic song.         --Milton.
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   5. An object of derision; a laughingstock.
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            And now am I their song, yea, I am their byword.
                                                  --Job xxx. 9.
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   6. A trifle; an insignificant sum of money; as, he bought it
      for a song. "The soldier's pay is a song." --Silliman.
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   Old song, a trifle; nothing of value. "I do not intend to
      be thus put off with an old song." --Dr. H. More.

   Song bird (Zool.), any singing bird; one of the Oscines.


   Song sparrow (Zool.), a very common North American sparrow
      (Melospiza fasciata, or Melospiza melodia) noted for
      the sweetness of its song in early spring. Its breast is
      covered with dusky brown streaks which form a blotch in
      the center.

   Song thrush (Zool.), a common European thrush (Turdus
      musicus), noted for its melodius song; -- called also
      mavis, throstle, and thrasher.
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   Syn: Sonnet; ballad; canticle; carol; canzonet; ditty; hymn;
        descant; lay; strain; poesy; verse.
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The Collaborative International Dictionary of English v.0.48:

Sparrow \Spar"row\, n. [OE. sparwe, AS. spearwa; akin to OHG.
   sparo, G. sperling, Icel. sp["o]rr, Dan. spurv, spurre, Sw.
   sparf, Goth. sparwa; -- originally, probably, the quiverer or
   flutterer, and akin to E. spurn. See Spurn, and cf.
   Spavin.]
   1. (Zool.) One of many species of small singing birds of the
      family Fringilligae, having conical bills, and feeding
      chiefly on seeds. Many sparrows are called also finches,
      and buntings. The common sparrow, or house sparrow, of
      Europe (Passer domesticus) is noted for its familiarity,
      its voracity, its attachment to its young, and its
      fecundity. See House sparrow, under House.
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   Note: The following American species are well known; the
         chipping sparrow, or chippy, the sage sparrow,
         the savanna sparrow, the song sparrow, the tree
         sparrow, and the white-throated sparrow (see
         Peabody bird). See these terms under Sage,
         Savanna, etc.
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   2. (Zool.) Any one of several small singing birds somewhat
      resembling the true sparrows in form or habits, as the
      European hedge sparrow. See under Hedge.
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            He that doth the ravens feed,
            Yea, providently caters for the sparrow,
            Be comfort to my age!                 --Shak.
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   Field sparrow, Fox sparrow, etc. See under Field,
      Fox, etc.

   Sparrow bill, a small nail; a castiron shoe nail; a
      sparable.

   Sparrow hawk. (Zool.)
      (a) A small European hawk (Accipiter nisus) or any of
          the allied species.
      (b) A small American falcon (Falco sparverius).
      (c) The Australian collared sparrow hawk (Accipiter
          torquatus).

   Note: The name is applied to other small hawks, as the
         European kestrel and the New Zealand quail hawk.

   Sparrow owl (Zool.), a small owl (Glaucidium passerinum)
      found both in the Old World and the New. The name is also
      applied to other species of small owls.

   Sparrow spear (Zool.), the female of the reed bunting.
      [Prov. Eng.]
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WordNet (r) 3.0 (2006):

song sparrow
    n 1: small songbird common in North America [syn: song
         sparrow, Melospiza melodia]