Mac 101: Mountain Lion's Magic Trackpad triple-finger tap dictionary lookup
Let's say you're reading TUAW and you see that I've used the word "peripatetic" in a post. While some of you would know the meaning of the word, others might be doing a bit of head-scratching and fire up the Dictionary app on your Mac. If you have a MacBook with a multi-touch trackpad or a desktop Mac with a Magic Trackpad, and if you run OS X Mountain Lion on your Mac, you can easily look up words with a simple gesture.
In whatever you happen to be looking at on your Mac, simply use three fingers to tap on the word that's causing you confusion. The word is highlighted in yellow, and a small popup shows you dictionary, thesaurus and Wikipedia entries that pertain to it. Sadly, this doesn't work with the Magic Mouse...
It's a fast way to look up words without missing a beat, so give that perplexing word a triple-finger tap the next time you're flummoxed or befuddled.