Scrub race

from The Collaborative International Dictionary of English v.0.48

Scrub \Scrub\ (skr[u^]b), a.
   Mean; dirty; contemptible; scrubby.
   [1913 Webster]

         How solitary, how scrub, does this town look!
                                                  --Walpole.
   [1913 Webster]

         No little scrub joint shall come on my board. --Swift.
   [1913 Webster]

   {Scrub game}, a game, as of ball, by unpracticed players.

   {Scrub race}, a race between scrubs, or between untrained
      animals or contestants.
      [1913 Webster]