Till Artha showed up in OSS Linux was lacking a perfect dictionary/thesaurus for long. Yes, it has WordNet as the lexicon and some primitive front ends such as kthesaurus and the native wordnet gui. Clearly it was not as usable as its Windows counterpart - WordWeb.
Artha is a handy dictionary/thesaurus program for Linux that focuses on high usability. It makes the best utilization of WordNet database with highly usable Hotkeys, Regular Expressions, Notifications, Relative Senses, Suggestions and Much More!
So, if your looking for a wordweb knockoff in desktop linux, look no further. Go, get Artha.