StarDict isn't actually a dictionary; rather, it's an interface to dictionary files, also freely downloadable from the Internet. StarDict is not without its quirks, but for its basic functionality -- looking up words -- it's fast and intuitive.
As StarDict is in the Ubuntu repositories, installation is quick and easy. There are several versions, though, appropriate to the windowing system you want to use, so choose carefully.
StarDict also needs dictionary files, and these you can download from the StarDict page on SourceForge. There are several free and open source dictionaries available; they can be used simultaneously with StarDict.
Since the dictionaries are compressed in BZ2 format, you can extract them using:
tar xjvf stardict-dictionary-name.tar.bz2
Then, just move the extracted directory to
The next time you start up StarDict, the said dictionary will be available. You don't really have to activate anything; StarDict picks them up automatically.
The version of StarDict from the repositories now includes Internet dictionary search as well as an interface to Google translate. Unfortunately, these don't really work so well and I've had the program momentarily freeze while it tried for a connection. I suggest you disable these added features and use StarDict exclusively as a local dictionary tool.