The Collaborative International Dictionary of English v.0.48:

Calabar \Cal"a*bar\, n.
   A district on the west coast of Africa.
   [1913 Webster]

   Calabar bean, The of a climbing legumious plant
      (Physostigma venenosum), a native of tropical Africa. It
      is highly poisonous. It is used to produce contraction of
      the pupil of the eye; also in tetanus, neuralgia, and
      rheumatic diseases; -- called also ordeal bean, being
      used by the negroes in trials for witchcraft.
      [1913 Webster]

WordNet (r) 3.0 (2006):

calabar bean
    n 1: dark brown highly poisonous seed of the calabar-bean vine;
         source of physostigmine and used in native witchcraft [syn:
         calabar bean, ordeal bean]