Actually, the longest non-scientific term is "floxinoxinihilipilification", which is the act of determining something as worthless. Another word that is fun (and useless) to know is "arachibutyrophobia", which is the extreme fear of having peanut butter stuck to the roof of your mouth.

Actually, it isn't the longest word in the dictionary. The longest word (in the unabridged English dictionary) is pneumonoultramicroscopicsilicovolcanoconiosis, which is a lung disease caused by breathing minute particles of silica dust. The definition of antidisestablishmentarianism is opposition to the withdrawal of state support or recognition from an established church, especially the Anglican Church in 19th-century England.