- any Australian tree of the genus Macadamia, especially M. ternifolia, having whorled leaves and elongated clusters of pink flowers.
- Also called macadamia nut. the edible, hard-shelled seed of this tree.
- any tree of the Australian proteaceous genus Macadamia, esp M. ternifolia, having clusters of small white flowers and edible nutlike seeds
- macadamia nut the seed of this tree
n.Australian evergreen tree, 1904, from Modern Latin (1858), named for Scotland-born chemist Dr. John Macadam (1827-1865), secretary of the Victoria Philosophical Institute, Australia.