The Collaborative International Dictionary of English v.0.48:

Scotch \Scotch\, a. [Cf. Scottish.]
   Of or pertaining to Scotland, its language, or its
   inhabitants; Scottish.
   [1913 Webster]

   Scotch broom (Bot.), the Cytisus scoparius. See Broom.


   Scotch dipper, or Scotch duck (Zool.), the bufflehead; --
      called also Scotch teal, and Scotchman.

   Scotch fiddle, the itch. [Low] --Sir W. Scott.

   Scotch mist, a coarse, dense mist, like fine rain.

   Scotch nightingale (Zool.), the sedge warbler. [Prov. Eng.]


   Scotch pebble. See under pebble.

   Scotch pine (Bot.) See Riga fir.

   Scotch thistle (Bot.), a species of thistle (Onopordon
      acanthium); -- so called from its being the national
      emblem of the Scotch.
      [1913 Webster]

WordNet (r) 3.0 (2006):

Scotch broom
    n 1: deciduous erect spreading broom native to western Europe;
         widely cultivated for its rich yellow flowers [syn: common
         broom, Scotch broom, green broom, Cytisus scoparius]