The Collaborative International Dictionary of English v.0.48:

Hyacinth \Hy"a*cinth\, n. [L. hyacinthus a kind of flower, prob.
   the iris, gladiolus, or larkspur, also a kind of gem, perh.
   the sapphire; as, a proper name, Hyacinthus, a beautiful
   Laconian youth, beloved by Apollo, fr. Gr. ?, ?: cf. F.
   hyacinthe. Cf. Jacinth. The hyacinth was fabled to have
   sprung from the blood of Hyacinthus, who was accidentally
   slain by Apollo.]
   1. (Bot.)
      (a) A bulbous plant of the genus Hyacinthus, bearing
          beautiful spikes of fragrant flowers. Hyacinthus
          orientalis is a common variety.
      (b) A plant of the genus Camassia (Camassia Farseri),
          called also Eastern camass; wild hyacinth.
      (c) The name also given to Scilla Peruviana, a
          Mediterranean plant, one variety of which produces
          white, and another blue, flowers; -- called also, from
          a mistake as to its origin, Hyacinth of Peru.
          [1913 Webster]

   2. (Min.) A red variety of zircon, sometimes used as a gem.
      See Zircon.
      [1913 Webster]

   Hyacinth bean (Bot.), a climbing leguminous plant
      (Dolichos Lablab), related to the true bean. It has dark
      purple flowers and fruit.
      [1913 Webster]

WordNet (r) 3.0 (2006):

hyacinth bean
    n 1: perennial twining vine of Old World tropics having
         trifoliate leaves and racemes of fragrant purple pea-like
         flowers followed by maroon pods of edible seeds; grown as
         an ornamental and as a vegetable on the Indian
         subcontinent; sometimes placed in genus Dolichos [syn:
         hyacinth bean, bonavist, Indian bean, Egyptian
         bean, Lablab purpureus, Dolichos lablab]