Look, this word isn't even close to being the longest word ever used, Aristophanes used the word Lopadotemachoselachogaleokranioleipsanodrimhypotrimmatosilphioparaomelitokatakechymenokichlepikossyphophattoperisteralektryonoptekephalliokigklopeleiolagoiosiraiobaphetraganopterygon, λοπαδοτεμαχοσελαχογαλεοκρανιολειψανοδριμυποτριμματοσιλφιοκαραβομελιτοκατακε-χυμενοκιχλεπικοσσυφοφαττοπεριστεραλεκτρυονοπτοκεφαλλιοκιγκλοπελειολαγῳοσιραιο-βαφητραγανοπτερύγων in the Greek alphabet
The first known written instance of floccinaucinihilipilification, as recorded in the Oxford English Dictionary, is in 1741, in a published letter by William Shenstone. The quotation is: "I loved him for nothing so much as his flocci-nauci-nihili-pili-fication of money." Other notable users of the word have included Robert Southey (in the Quarterly Review 14:334, 1816), and Walter Scott (Journal 18, 1829). Scott, however, replaced the "nauci" component with "pauci". The feminine noun construction, floccinaucinihilipilificatrix, can be found in the Robert Heinlein novel The Number of the Beast. Wikipedia.
Neither of these words is legal in Scrabble.