UPDATE: I ditched Babiloo for Artha Dictionary. It has a lot more cool features and is perhaps the best available offline dictionary currently. It’s available in the Ubuntu software centre as well.
Lately I was using the Dictionary that comes as an accessory bundled with Ubuntu. It was good, but I thought it’d be wonderful to have an offline one.
After a lot of trials and errors, I settled with Babiloo. It’s a simple app which is available in the Ubuntu Software Centre as well. Several free dictionaries can be downloaded from here and installed in Babiloo. So far so good.
P.S. And I’m beginning to love the Longman Dictionary of Contemporary English (which can be downloaded from the above link).
EDIT: The above link to download dictionaries doesn’t seem to work anymore. You can download free dictionaries from this link.