Source : Webster's Revised Unabridged Dictionary (1913)

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}.]

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.

   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, {D. Lablab}; the common
         haricot beans, kidney beans, string beans, and pole
         beans, all included in {Phaseolus vulgaris}; the lower
         bush bean, {Ph. vulgaris}, variety {nanus}; Lima bean,
         {Ph. lunatus}; Spanish bean and scarlet runner, {Ph.
         maltiflorus}; Windsor bean, the common bean of England,
         {Faba vulgaris}. As an article of food beans are
         classed with vegetables.

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

   {Bean aphis} (Zo["o]l.), a plant louse ({Aphis fab[ae]})
      which infests the bean plant.

   {Bean fly} (Zo["o]l.), a fly found on bean flowers.

   {Bean goose} (Zo["o]l.), a species of goose ({Anser
      segetum}).

   {Bean weevil} (Zo["o]l.), a small weevil that in the larval
      state destroys beans. The American species in {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}.

Source : WordNet®

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: {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 tree}, {Coumarouna odorata}, {Dipteryx
        odorata}]