The Collaborative International Dictionary of English v.0.48:

Poison bush \Poison bush\ In Australia:
      (a) Any fabaceous shrub of the genus Gastrolobium, the
          herbage of which is poisonous to stock; also, any
          species of several related genera, as Oxylobium,
          Gompholobium, etc.
      (b) The plant Myoporum deserti, often distinguished as
          Ellangowan poison bush or dogwood poison bush.
      (c) The ulmaceous plant Trema cannabina, which, though
          not poisonous, is injurious to stock because of its
          large amount of fiber.
          [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

poison bush
    n 1: any of various Australian evergreen shrubs of the genus
         Gastrolobium having whorled compound leaves poisonous to
         livestock and showy yellow to deep reddish-orange flowers
         followed by two-seeded pods [syn: poison bush, poison
         pea, gastrolobium]
    2: either of two Australian plants of the genus Swainsona that
       are poisonous to sheep [syn: darling pea, poison bush]