This Service adds any unique words you look up in the OS X Dictionary app to a TextEdit document that is- saved on your desktop, so that you can review, or repeat them later. Then you can use the same service to look up those words that you have logged already; they won't be added to your log file.
The service is seamlessly integrated with the Dictionary service on your Mac. It is even installed on the same keyboard shortcut: Command-Control-D.
The only limitation is that it only works with selected text, so if you are looking up a word by hovering the cursor over it, in, say, Preview or Safari, then you'll have to choose More in the lower right corner of the Dictionary sheet that pops up to view the full Dictionary window. Then you'll have to press Command-Control-D once more, to "log" the word into the text file (the search word turns up selected in the Dictionary window.)
Avoid the above limitation by selecting the word before Command-Control-D. If you select the word before pressing Command-Control-D, then everything is handled automatically.
Since English is not my native language, this is something I have been wanting for years. So it is mostly made for non-native English speaker, but may also be useful for native anglophones.
How to install:
Choose service and don't check anything
Search for the Run AppleScript action, and add it to your Service
Paste in the script below, replacing everything that is by default in the Run AppleScript action
Save the Service as dictLogger
Open the Keyboard preferences of the System Preferences pane
Find the service under "Services" and install it with the keyboard shortcut Command-Control-D
After you have successfully looked up a word, look into the file "DictLogger.txt" that should be on your Desktop if everything is working
Select a word in "DictLogger.txt", to see that it works from here
If you use some app other than TextEdit for .txt files, be sure to set the default app of this file to TextEdit, if you want it to open with TextEdit. I don't guarantee that every other text editor will work, though I think it will work with TextWrangler and BBEdit
Mac OS X Hints