octosyllabic

from WordNet (r) 3.0 (2006)

octosyllabic
    adj 1: having or characterized by or consisting of eight
           syllables

from The Collaborative International Dictionary of English v.0.48

Octosyllabic \Oc`to*syl*lab"ic\, Octosyllabical
\Oc`to*syl*lab"ic*al\, a. [L. octosyllabus. See {Octo-}, and
   {Syllable}.]
   Consisting of or containing eight syllables.
   [1913 Webster]