Definitionist: One who makes definitions. This includes any and all of the wonderful people who've ever added a definition to Urban Dictionary. These people take delight in redefining the liquid, shifting creation that is the English language, either by reworking antiquated words and giving them dynamic new meanings, or else creating entirely new words. It's definitionists we have to thank for such excellent words as: Cool, Posse, Grippa, and basically anything with gratuitous "th"s, "q"s or "y"s, such as "quoth", "thy", "thou", "quip", "hast", and "thine".
Casual Reader: Dang, some of those definitionists really need to find something else to do...
Intelligent Person: Are you kidding? It's definitionists that we have to thank for no longer using the language of the 18th century! I don't know about you, but I don't think that talking like I'm in a Shakespeare play is very cool.
Casual Reader: Wow, you're right! You know what? I'm going to become a definitionist today!