Dictionary Shortcuts

MacWorld just ran a very cool article that nearly slipped past me but turns out to be full of great little shortcuts.

This one was really cool, though let's see if I can remember the keyboard shortcut....

4. Use pop-up definitions

In many Mac programs, you can hover your cursor over a word and press Control-Command-D to see this definition balloon appear.One of my favorite OS X features, and one that too few people take advantage of, is systemwide pop-up definitions. In most recent Mac applications—including Safari, Mail, and most other programs that display text or let you edit text—just position the cursor over the word you want to define and then press Control-Command-D. A floating balloon appears containing the definition(s) of that word.
You can switch to the Thesaurus entries for that word using the pop-up menu at the bottom of the balloon, and clicking More will open the Dictionary application and look up the word.

A nice touch is that if you hold down Control-Command-D while you move the cursor around the screen, the definition balloon updates continuously to display information about whichever word is beneath the cursor.