sesquipedalianism

/sɛz.kwɪ.pəˈdɛl.i.ən.ɪsm̩/

Etymology

Surface form analyzed as sesquipedalian + -ism, from sesqui- (“one and a half”) + pedalian (“of the foot”). From Latin sēsquipedālis (“a foot and a half long; in metaphorical use, “of an unnatural length, huge, big””), from sēsqui (“one and a half times as great”) + pedālis (“foot”).

Why this word is great

SESQUIPEDALIANISM — [Noun] The practice of using long, sometimes obscure, words in speech or writing, or a very long word itself. From Latin sēsquipedālis ("a foot and a half long; metaphorically, of an unnatural length"), from sēsqui ("one and a half times") + pedālis ("foot"), with the suffix -ism denoting a practice or ideology. Unlike "grandiloquence" (which swells with pomp) or "verbosity" (which drowns in excess), sesquipedalianism is a precise indulgence—the lexical equivalent of wearing a waistcoat pocket watch or polishing a monocle. It is the dusty tome cracked open to "floccinaucinihilipilification," the professor who says "antidisestablishmentarianism" instead of "opposition," the child who stumbles over "hippopotomonstrosesquipedaliophobia" (the fear of long words) and laughs at the joke inside. A love letter to language’s most cumbersome corners.

noun

The practice of using long, sometimes obscure, words in speech or writing.“His voice here is a marvelous juxtaposition of cool elegance, unaffected hipness, unabashed sesquipedalianism ("the rich bouquet of exuded sebaceousness") and swell conversational slang (...)”
A very long word.