The Dictionary application received a number of improvements with the release of OS X 10.5. First of all, there’s a new technical jargon dictionary from Apple, and direct access to Wikipedia entries as well. There’s also a huge resource known as “front and back matter,” which you can reach by selecting Go -> Front/Back Matter -> New Oxford American Dictionary from Dictionary’s menu. In the front/back matter, you’ll find things such as a list of all US presidents, a chemical elements chart, standard weights and measures, countries of the world, and much more. If you haven’t checked it out yet, it’s quite impressive in its breadth.
But none of the above are really secret features of the new Dictionary—they’re covered in Help, as well as on Apple’s 300 features page. Something that’s not covered there, however, is the fact that you can rename the labels for each dictionary—that is, the row of labels that appears at the top of the Dictionary window. By default, you’ll see five labels there—All, Dictionary, Thesaurus, Apple, and Wikipedia. While you can’t change All, you can change any of the other labels to anything you desire. Change Wikipedia to Wondrous Wiki; Apple to Apple Tech Lingo; Thesaurus to Similar Words; or whatever you desire.
Feel free to use whatever names suit your fancy, but as seen in the screen shot above, longer words will obviously lead to a wider row in Dictionary. But if you’ve got screen real estate to spare, go ahead and have some fun with your dictionary labels.