Source : Webster's Revised Unabridged Dictionary (1913)

Souari nut \Sou*a"ri nut`\ (Bot.)
   The large edible nutlike seed of a tall tropical American
   tree ({Caryocar nuciferum}) of the same natural order with
   the tea plant; -- also called {butternut}. [Written also
   {sawarra nut}.]

Butternut \But"ter*nut`\, n.
   1. (Bot.) An American tree ({Juglans cinerea}) of the Walnut
      family, and its edible fruit; -- so called from the oil
      contained in the latter. Sometimes called {oil nut} and
      {white walnut}.

   2. (Bot.) The nut of the {Caryocar butyrosum} and {C.
      nuciferum}, of S. America; -- called also {Souari nut}.

Source : WordNet®

souari nut
     n 1: large South American evergreen tree trifoliate leaves and
          drupes with nutlike seeds used as food and a source of
          cooking oil [syn: {souari}, {souari tree}, {Caryocar
          nuciferum}]
     2: a large nutlike seed of a South American tree