The Collaborative International Dictionary of English v.0.48:

macadamia nut \macadamia nut\ n.
   The hard-shelled nut of the Macadamia ternifolia, or the
   delicious edible nut without its shell; large quantities are
   produced in Hawaii and sold commercially.
   [PJC]

WordNet (r) 3.0 (2006):

macadamia nut
    n 1: small Australian tree with racemes of pink flowers; widely
         cultivated (especially in Hawaii) for its sweet edible nuts
         [syn: macadamia nut, macadamia nut tree, Macadamia
         ternifolia]
    2: nutlike seed with sweet and crisp white meat