From The Collaborative International Dictionary of English v.0.48 :
Polysyllabic \Pol`y*syl*lab"ic\, Polysyllabical
\Pol`y*syl*lab"ic*al\, a. [Gr. ?; poly`s many + ? syllable: cf.
F. polysyllabique.]
Pertaining to a polysyllable; containing, or characterized
by, polysyllables; consisting of more than three syllables.
[1913 Webster]
From WordNet (r) 2.0 :
polysyllabic
adj 1: having or characterized by words of more than three
syllables
2: (of words) long and ponderous; having many syllables;
"sesquipedalian technical terms" [syn: sesquipedalian]