The Collaborative International Dictionary of English v.0.48:

macadamia \macadamia\ n.
   1. any tree of the genus Macadamia, especially Macadamia
      ternifolia.

   Syn: macadamia tree.
        [WordNet 1.5]

   2. A macadamia nut.
      [PJC]

WordNet (r) 3.0 (2006):

macadamia
    n 1: any tree of the genus Macadamia [syn: macadamia,
         macadamia tree]