Many people don't know this, but in most applications on MacOSX "Tiger" you can see the definition or synonym of a word instantly. Here's how it works:
Enjoy!
- Hover the cursor over the word you want to learn more about
- Hold down Command (Apple Key) + Control + D
- A pop-up will appear above the word with the definition
- If you want to see the synonym, click where it shows the name of the dictionary, at the top of the pop-up window, and select Thesaurus. If the pop-up goes away, repeat step 2 quickly (without holding down the keys long).
Enjoy!

Wow, thanks for the cool tip!