This doesn't relate directly to books, or does it...? Well, anyways, I was on dictionary.com, and I saw this, and so I thought, "Hey, why don't I enlighten the rest of the world?":
The word, in addition to being the largest word held on Dictionary.com, is: "an obscure term ostensibly referring to a lung disease caused by silica dust, sometimes cited as one of the longest words in the English language," as quoted from http://www.dictionary.com/.
So, if you ever have the urge to get back at that coughing fool who never coughs into their shoulder like a good sensible person but into the open air, inviting others to become ill like them, say, adopting concern, "Do you have pneumonoultramicroscopicsilicovolcanoconiosis?" But remember to have the definition down, 'cause they might just ask, "What does that mean?"
Today's word of the day(on Dictionary.com), by the way, is heliolatry, which means, "worship of the sun."