I happen to like stardict (
http://www.stardict.org ) for a dictionary program. If you prefer a command line version, there's sdcv (
http://sdcv.sourceforge.net ). There are several others that use different screen libraries and dependencies. Many use different dictionary formats. These types of programs are for look up of words offline (although some are tied to the Internet too). They shouldn't be confused with a spell-checking program. For that, I'm currently using hunspell (
http://hunspell.sourceforge.net ).