WebDicty

WebDicty is the a free multilingual dictionary. It has preconfigured a number of on-line Web dictionaries for Spanish, English, German, French, Italian, Catalan, Basque, Portuguese and Dutch including definition and translation dictionaries.

WebDicty does not have a list of words or a local dictionary. Instead, it relies on the freely available dictionaries on the web. Every time you type a word to look it up, WebDicty connects to the selected webpage, gets the answer, filters it an processes it so that is easy to read, removing embedded or pop-up ads. So it is basically a browser of preset pages (the dictionaries) with internal filters to remove the unwanted information. You can also open the actual webpage in your browser from within WebDicty by clicking on the browser button (the world icon).

WebDicty stays iconized on the task bar when minimized. It can be launched by pressing ALT+F10 from any application and it will automatically look for the word that is selected in that application in the current dictionary. Besides, double clicking on any word in the results of WebDicty (both right and left panel) will make WebDicty search for that word in the current dictionary. It also accepts some command line arguments:
/m launch minimized (iconized, in fact)
/w‹word› look for ‹word›
/f‹n› start with language from number ‹n›
/t‹n› start with language to number ‹n›
/d‹n› start with dictionary number ‹n› within the default or defined category

You can put it on your Start menu with /m so that it is autostarts (iconized) with Windows.