Is there an offline dictionary?
Are there any off-line dictionaries available?
Solution 1:
I would recommend Artha, It is an Offline dictionary, I find it really comprehensive and it also suggests you synonyms of the word you are looking up.
You can download Artha from Ubuntu Software Centre.
Artha is a free cross-platform English thesaurus that works completely off-line and is based on WordNet
Website: http://artha.sourceforge.net
Solution 2:
I suggest the GoldenDict (Click to Install) - a very powerful shell, where you will be able to install a great many dictionaries of various formats. Just for English explanatory dictionary just add goldendict-wordnet option (Click to Install).