Want a really good dictionary or a computing medical dictionary how about a Thesaurus?
The Free online Dictionary has this and much more, it is very easy to use. You don't have to pay or even register. just go there, type in your word and press search, it's great.
Here's the link:
http://www.thefreedictionary.comIve, never had any problems with it, I hope you find it as useful as I do!
Sheba