Hey you can try the fantastic Stardict from here:
http://stardict.sourceforge.net/You'll also get lots of free dictionaries, encyclopedias, jargon list, thesauruses etc from there. Its a cross platform dictionary so you can use the same on windows too. Actually its not a dictionary on its own it is just a frontend to display the dictionaries. Personally found it better than wordweb.
Let me know how it goes.
Gautam Chaudhari.