1) Multisyllable 2) Sesquipedalia 1) Polysyllabic word 2) Word 
• (n.) A word of many syllables, or consisting of more syllables than three; -- words of less than four syllables being called monosyllables, dissyllables, and trisyllables.
Pol'y·syl`la·ble noun [ Poly- + syllable .] A word of many syllables, or consisting of more syllables than three; -- words of less than four syllables being called monosyllables , dissyllables , and trisyllables . 
[n] - a word of more than three syllables
polysyllable, polysyllabic, polysyllabicism Having many (at least three or more) syllables.
polysyllabic word noun a word of more than three syllables