Source : Webster's Revised Unabridged Dictionary (1913)

Guaiacum \Gua"ia*cum\, n. [NL., fr. Sp. guayaco, from native
   name in Hayti.]
   1. (Bot.) A genus of small, crooked trees, growing in
      tropical America.

   2. The heart wood or the resin of the {Guaiacum offinale} or
      lignum-vit[ae], a large tree of the West Indies and
      Central America. It is much used in medicine. [Written
      also {guaiac}.]

Source : WordNet®

guaiacum
     n 1: medicinal resin from the lignum vitae tree
     2: hard greenish-brown wood of the lignum vitae tree and other
        trees of the genus Guaiacum [syn: {lignum vitae}, {guaiac}]
     3: small genus of evergreen resinous trees or shrubs of warm
        and tropical America [syn: {genus Guaiacum}]