The Collaborative International Dictionary of English v.0.48:

eucalyptol \eu`ca*lyp*tol\, n. [eucalyptus + L. oleum oil.]
   (Chem.)
   A volatile, terpenelike oil (C10H18O), which is the main
   constituent of the oil of eucalyptus. It has cockroach
   repellent activity and is used as a flavoring aid in
   pharmaceuticals. Chemically it is
   1,3,3-trimethyl-2-oxabicyclo-[2,2,2]-octane. --MI11

   Syn: cineole, cajeputol. [1913 Webster +PJC]

   Note: In the 1913 Webster eucalytpol was defined as an oil
         "consisting largely of cymene". Cymene
         (isopropyltoluene, C10H14) differs from that of the
         substance currently called eucalyptol, in having an
         unsaturated ring and no oxygen. Para-cymene does occur
         in eucalyptus oil as well as some other essential oils.
         [PJC]