1. [n]  a very long word (a foot and a half long)
2. [adj]  (of words) long and ponderous; having many syllables; "sesquipedalian technical terms"
3. [adj]  given to the overuse of long words; "sesquipecalian orators"; "this sesquipedalian way of saying one has no money"

SESQUIPEDALIAN is a 14 letter word that starts with S.