A word having more than one syllable
(of a word) Having more than one syllable; having multiple or many syllables.
"Antidisestablishmentarianism" definitely qualifies as a polysyllabic word.
(of spoken or written language) Characterized by or consisting of words having numerous syllables.
I have a particularly off-putting predilection for the utilization of ponderously polysyllabic linguistic constructions.