The Collaborative International Dictionary of English v.0.48:

Guiacol \Gui"a*col\, n. [Guiac + -ol.] (Chem.)
   A colorless liquid, C6H4.OCH3.OH, resembling the phenols,
   found as a constituent of woodtar creosote, and produced by
   the dry distillation of guaiac resin.
   [1913 Webster]