How do you spell pseudoantidisestablishmentarianism?

You're right to be suspicious! "Pseudoantidisestablishmentarianism" is a made-up word.

It's a humorous example of how long and complex words can be formed in English. There's no real meaning behind it, but it sounds like a real word, which makes it funny.

If you want to learn more about real long words, try looking up "pneumonoultramicroscopicsilicovolcanoconiosis" (a lung disease caused by inhaling very fine silica dust). It's a real word, although not as commonly used as "antidisestablishmentarianism" (opposition to the separation of church and state).