Pneumonoultramicroscopicsilicovolcanoconiosis (45)- “a factitious word alleged to mean ‘a lung disease caused by the inhalation of very fine silica dust, causing inflammation in the lungs.’” – technical term

Antidisestablishmentarianism (28) – a political position that originated in nineteenth-century Britain in opposition to proposals for the disestablishment of the Church of England, that is, to remove the Anglican Church’s status as the state church of England, Ireland and Wales. longest non technical term

“Supercalifragilisticexpialidocious“, the 34-letter title of a song from the movie Mary Poppins. It does appear in several dictionaries, but only as a proper noun defined in reference to the song title. The attributed meaning is “a word that you say when you don’t know what to say.”