The Collaborative International Dictionary of English v.0.48:

Oleander \O`le*an"der\, n. [F. ol['e]andre (cf. It. oleandro,
   LL. lorandrum), prob. corrupted, under the influence of
   laurus laurel, fr. L. rhododendron, Gr. ?; ? rose + ? tree.]
   (Bot.)
   A beautiful evergreen shrub (Nerium oleander) of the
   Dogbane family, having clusters of fragrant red, white, or
   pink flowers. It is a native of the East Indies, but the red
   variety has become common in the south of Europe. Called also
   rosebay, rose laurel, and South-sea rose.
   [1913 Webster +PJC]

   Note: Every part of the plant is dangerously poisonous, and
         death has occured from using its wood for skewers in
         cooking meat.
         [1913 Webster]

WordNet (r) 3.0 (2006):

oleander
    n 1: an ornamental but poisonous flowering shrub having narrow
         evergreen leaves and clusters of fragrant white to pink or
         red flowers: native to East Indies but widely cultivated in
         warm regions [syn: oleander, rose bay, Nerium
         oleander]