Source : Webster's Revised Unabridged Dictionary (1913)

Scrub \Scrub\, n.
   1. One who labors hard and lives meanly; a mean fellow. ``A
      sorry scrub.'' --Bunyan.

            We should go there in as proper a manner possible;
            nor altogether like the scrubs about us.
                                                  --Goldsmith.

   2. Something small and mean.

   3. A worn-out brush. --Ainsworth.

   4. A thicket or jungle, often specified by the name of the
      prevailing plant; as, oak scrub, palmetto scrub, etc.

   5. (Stock Breeding) One of the common live stock of a region
      of no particular breed or not of pure breed, esp. when
      inferior in size, etc. [U.S.]

   {Scrub bird} (Zo["o]l.), an Australian passerine bird of the
      family {Atrichornithid[ae]}, as {Atrichia clamosa}; --
      called also {brush bird}.

   {Scrub oak} (Bot.), the popular name of several dwarfish
      species of oak. The scrub oak of New England and the
      Middle States is {Quercus ilicifolia}, a scraggy shrub;
      that of the Southern States is a small tree ({Q.
      Catesb[ae]i}); that of the Rocky Mountain region is {Q.
      undulata}, var. Gambelii.

   {Scrub robin} (Zo["o]l.), an Australian singing bird of the
      genus {Drymodes}.

Source : WordNet®

scrub bird
     n : small fast-running Australian bird resembling a wren and
         frequenting brush or scrub [syn: {scrubbird}, {scrub-bird}]