QUOTE : The one that every lexicographer offers as proof is "antidisestablishmentarianism." It's a word plenty of people are familiar with, but most of our citational evidence for it is in lists of long words, not in running prose, and when it does appear in running prose, it appears in sentences like "'Antidisestablishmentarianism' is a long word." When tasked with prying meaning out of a bunch of citations like that, you quickly discover that "antidisestablishmentarianism" is rarely ascribed a meaning in text. It's not the only one. "Pneumonoultramicroscopicsilicovolcanoconiosis" - a word that puzzlers and lexicographers call "P45" - sure looks like and sounds like the name of a great disease, and it is entered in our Webster's New International Dictionary, Second Edition, but it does not have any meaningful use. In fact, it appears to have been coined by the president of the National Puzzler's League in 1935 just to see if dictionaries would fall for it. We did. We're a little more careful now.