A word that's so long that I had to make a space within it so the example for this definition would be accepted. What's more, it's the longest word in the English language. Basically, pneumonoultramicropscopicsilicovolcano coniosis a lung disease caused by breathing in particles of siliceous volcanic dust. Invented by some guy who had too much time on his hands and wanted to make history by creating the longest word ever.
Doctor: Sir, I am afraid you have come down with a severe case of pneumonoultramicropscopicsilicovolcano coniosis due to exposure to volcanic dust.