sometimes i needed for a desktop dictionary on ubuntu linux, now i found how to setup the arabic dictionary in the linux Dictionary:

for gnome :

- open Applications Menu -> Accessories -> Dictionary.

- the Dictionary application is opened. now click edit menu and select Preferences.

- in the source tab click Add button.

- A new window opened, in the Description field write: Arabic Dictionary. or whatever you want to name it.

- let Transport select box as Transport.

- Hostname : dict.arabeyes.org

- Port: 2628

now enjoy using the desktop dictionary.