The Collaborative International Dictionary of English v.0.48:

mallee \mal"lee\, n. [Native name.]
   1. (Bot.) A dwarf Australian eucalypt with a number of thin
      stems springing from a thickened stock. The most common
      species are Eucalyptus dumosa and Eucalyptus Gracilis.
      [Webster 1913 Suppl.]

   2. Scrub or thicket formed by the mallee. [Australia]
      [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

Eucalyptus dumosa
    n 1: small shrubby mallee [syn: white mallee, congoo mallee,
         Eucalyptus dumosa]