The Collaborative International Dictionary of English v.0.48:

Jacinth \Ja"cinth\, n. [F. jacinthe, L. hyacinthus. See
   Hyacinth.]
   See Hyacinth. --Tennyson.
   [1913 Webster]

WordNet (r) 3.0 (2006):

jacinth
    n 1: a red transparent variety of zircon used as a gemstone
         [syn: hyacinth, jacinth]