The Collaborative International Dictionary of English v.0.48:

Palma Christi \Pal"ma Chris"ti\ [L., palm of Christ.] (Bot.)
   A plant (Ricinus communis) with ornamental peltate and
   palmately cleft foliage, growing as a woody perennial in the
   tropics, and cultivated as an herbaceous annual in temperate
   regions; -- called also castor-oil plant. [Sometimes
   corrupted into palmcrist.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Castor oil \Cas"tor oil\ (k[a^]s"t[~e]r oil`).
   A mild cathartic oil, expressed or extracted from the seeds
   of the Ricinus communis, or Palma Christi. When fresh the
   oil is inodorous and insipid.
   [1913 Webster]

   Castor-oil plant. Same as Palma Christi.
      [1913 Webster]

WordNet (r) 3.0 (2006):

castor-oil plant
    n 1: large shrub of tropical Africa and Asia having large
         palmate leaves and spiny capsules containing seeds that are
         the source of castor oil and ricin; widely naturalized
         throughout the tropics [syn: castor-oil plant, castor
         bean plant, palma christi, palma christ, Ricinus
         communis]