I searched all over to find an offline dictionary solution to meet my needs, since I'm often in need of a dictionary and thesaurus I can use offline. Having not found an adequate solution in OpenDict (its dictionaries are only for foreign languages like Latvian and its website is inundated with spam), Stardict (it's bloated, written in bad English, and generally annoying to use) or other programs, and not always having access to the internet whenever I need a dictionary, I figured out how to set up a local DICT server and thereby use the Dictionary program that's already included with Ubuntu to access locally stored dictionaries. It's not all that difficult, it turns out.
First, install DictD:
this installs a DICT server. now you can install whatever dictionaries you want. Dictionaries are in the repos, here's a list I found using a package search:
sudo apt-get install dictd
so to install a thesaurus, for example, use
Now to configure Dictionary, open the Dictionary program (in <Hardy it's in Accessories, in Intrepid it's under Office), go into Edit -> Preferences, click on "Add" to add a source, then under "Description" give it a name like "Local Dictionaries," under "hostname" type "localhost" [EDIT: In Jaunty and later you might try putting "127.0.0.1" (without the quotes) instead; see below] and leave the port number the same. Now click "add" and now whenever you're offline you can choose "Local Dictionaries" from "Dictionary Sources" and access your dictionaries offline!
sudo apt-get install dict-moby-thesaurus