WordNet sense 1 (a very long word (a foot and a half long)):

sesquipedalia

WordNet sense 2 (making claim to or creating an appearance of (often undeserved) importance or distinction):

pretentious

WordNet sense 3 ((of words) long and ponderous; having many syllables):

polysyllabic

WordNet sense 4 (primarily spatial sense; of relatively great or greater than average spatial extension or extension as specified):

long