The Collaborative International Dictionary of English v.0.48:

Thrush \Thrush\, n. [OE. [thorn]rusche, AS. [thorn]rysce; akin
   to OHG. drosca, droscea, droscela, and E. throstle. Cf.
   Throstle.]
   1. (Zool.) Any one of numerous species of singing birds
      belonging to Turdus and allied genera. They are noted
      for the sweetness of their songs.
      [1913 Webster]

   Note: Among the best-known European species are the song
         thrush or throstle (Turdus musicus), the missel
         thrush (see under Missel), the European redwing, and
         the blackbird. The most important American species are
         the wood thrush (Turdus mustelinus), Wilson's thrush
         (Turdus fuscescens), the hermit thrush (see under
         Hermit), Swainson's thrush (Turdus Aliciae), and
         the migratory thrush, or American robin (see Robin).
         [1913 Webster]

   2. (Zool.) Any one of numerous species of singing birds more
      or less resembling the true thrushes in appearance or
      habits; as the thunderbird and the American brown thrush
      (or thrasher). See Brown thrush.
      [1913 Webster]

   Ant thrush. See Ant thrush, Breve, and Pitta.

   Babbling thrush, any one of numerous species of Asiatic
      timaline birds; -- called also babbler.

   Fruit thrush, any species of bulbul.

   Shrike thrush. See under Shrike.

   Stone thrush, the missel thrush; -- said to be so called
      from its marbled breast.

   Thrush nightingale. See Nightingale, 2.

   Thrush tit, any one of several species of Asiatic singing
      birds of the genus Cochoa. They are beautifully colored
      birds allied to the tits, but resembling thrushes in size
      and habits.

   Water thrush.
      (a) The European dipper.
      (b) An American warbler (Seiurus Noveboracensis).
          [1913 Webster]

WordNet (r) 3.0 (2006):

thrush nightingale
    n 1: large nightingale of eastern Europe [syn: thrush
         nightingale, Luscinia luscinia]