Offline English thesaurus based on WordNethttp://artha.sourceforge.net/
Artha is a free cross-platform English thesaurus that works
completely off-line and is based on WordNet. Stable releases for
download are currently available for GNU/Linux and Microsoft Windows;
it is tested on major Desktop Environments like GNOME, KDE, Xfce, etc
and on Microsoft Windows XP, Vista and 7. Artha is released under the
GNU General Public Licence version 2.