The Collaborative International Dictionary of English v.0.48:

Tonka bean \Ton"ka bean`\ [Cf. F. onca, tonka.] (Bot.)
   The seed of a leguminous tree (Dipteryx odorata), native of
   Guiana. It has a peculiarly agreeable smell, and is employed
   in the scenting of snuff. Called also tonquin bean.
   [Written also tonca bean, tonga bean.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Bean \Bean\ (b[=e]n), n. [OE. bene, AS. be['a]n; akin to D.
   boon, G. bohne, OHG. p[=o]na, Icel. baun, Dan. b["o]nne, Sw.
   b["o]na, and perh. to Russ. bob, L. faba.]
   1. (Bot.) A name given to the seed of certain leguminous
      herbs, chiefly of the genera Faba, Phaseolus, and
      Dolichos; also, to the herbs.
      [1913 Webster]

   Note: The origin and classification of many kinds are still
         doubtful. Among true beans are: the black-eyed bean and
         China bean, included in Dolichos Sinensis; black
         Egyptian bean or hyacinth bean, Dolichos Lablab; the
         common haricot beans, kidney beans, string beans, and
         pole beans, all included in Phaseolus vulgaris; the
         lower bush bean, Phaseolus vulgaris, variety nanus;
         Lima bean, Phaseolus lunatus; Spanish bean and
         scarlet runner, Phaseolus multiflorus; Windsor bean,
         the common bean of England, Faba vulgaris.
         [1913 Webster] As an article of food beans are classed
         with vegetables.
         [1913 Webster]

   2. The popular name of other vegetable seeds or fruits, more
      or less resembling true beans.
      [1913 Webster]

   Bean aphis (Zool.), a plant louse (Aphis fab[ae]) which
      infests the bean plant.

   Bean fly (Zool.), a fly found on bean flowers.

   Bean goose (Zool.), a species of goose (Anser segetum).


   Bean weevil (Zool.), a small weevil that in the larval
      state destroys beans. The American species is Bruchus
      fab[ae].

   Florida bean (Bot.), the seed of Mucuna urens, a West
      Indian plant. The seeds are washed up on the Florida
      shore, and are often polished and made into ornaments.

   Ignatius bean, or St. Ignatius's bean (Bot.), a species
      of Strychnos.

   Navy bean, the common dried white bean of commerce;
      probably so called because an important article of food in
      the navy.

   Pea bean, a very small and highly esteemed variety of the
      edible white bean; -- so called from its size.

   Sacred bean. See under Sacred.

   Screw bean. See under Screw.

   Sea bean.
      (a) Same as Florida bean.
      (b) A red bean of unknown species used for ornament.

   Tonquin bean, or Tonka bean, the fragrant seed of
      Dipteryx odorata, a leguminous tree.

   Vanilla bean. See under Vanilla.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Dipteryx \Dipteryx\ n.
   a genus of tropical American trees which produce a black seed
   called the tonka bean.

   Syn: Coumarouna, genus Coumarouna, genus Dipteryx.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

tonka bean
    n 1: fragrant black nutlike seeds of the tonka bean tree; used
         in perfumes and medicines and as a substitute for vanilla
         [syn: tonka bean, coumara nut]
    2: tall tropical South American tree having pulpy egg-shaped
       pods of fragrant black almond-shaped seeds used for flavoring
       [syn: tonka bean, tonka bean tree, Coumarouna odorata,
       Dipteryx odorata]