A bewildering array of on-screen dictionary utilities, many with equally bewilderingly similar names, are available for Linux. Most are geared unashamedly to casual users, and in their simplest form are little more than a nice input box linked to a two-column word list; with an increasing number of professional-standard CAT tools available for Linux, utilities of this kind have lost any attraction they may have had. Some applications are coupled to dictionaries of varying usefulness; few offer professional-level language content, although the automatic lookup function of some utilities can be useful, for instance when used within a web browser. Spelling dictionaries are also available.
Unless otherwise stated, the utilities listed below are free/open source. Most have been written by individuals or very small teams without substantial resources. One consequence is that installation can sometimes be something of an adventure - failed dependencies are a common occurrence, installation instructions are often written in geeky language, and some tweaking may be required for particular system configurations. On the other hand, the open source applications can be freely modified by anyone with the necessary programming skills.
A feature-rich dictionary lookup program project. Thanks to Maxime Boisset for drawing attention to this.
GUI utility for dictionaries in the old Babylon *.dic format (not the new *.dat/*.bgl formats). Interfaces to the clipboard for automatic look-up. Does not support fuzzy matches.
Dictd is variously described as a daemon, dictionary server, utility, etc., and is an application designed to provide access, within a client/server setup, to dictionaries which comply with the dict protocol. It can be used in a desktop installation, however.
A number of GUI front-ends are available for use with dictd, notably Kdict and Wordinspector.
GUI dictionary utility; makes use of grep to permit fuzzy searching. Supplied with a general German/English dictionary containing some 120,000 terms. User dictionaries can be created. Written in Tcl/Tk.
Russian translators in particular might like to take a look at this one. Even if your Russian is as rudimentary as mine or for that matter non-existent, though, don't be put off by the seemingly obfuscating instructions: this utility, actually a collection of Tcl console scripts and a Tk interface, is likely to be easier to install than it looks. Supports fuzzy searching. EnRus comes with its own Russian/English dictionary, and you can add your own terms or create your own dictionaries - with or without Russian content.
Freedict is a collection of dictionaries which can be accessed using software which supports the Dict protocol. The dictionaries themselves are likely to be of only casual interest to professionals: although there is quite a large selection of languages, the number of words in most of the dictionaries doesn't even reach five figures.
Spelling utility of the GNU project. Spellcheck dictionaries available for a huge number of languages.
English/Chinese Dictionary written by Daniel Gau using python/gtk, based upon xdict.
Command-line dictionary utility (Steak) with optional GUI (KSteak for KDE, GSteak for GNOME). Supplied with its own German/English dictionary; users can add their own entries.
GUI dictionary utility. Interfaces to the clipboard for automatic lookup. Supports dictionaries in plain (two-column list), Babylon *.dic and binary encoded) format.
Wordtrans is a command-line dictionary utility which can be used to access dictionaries in the i2e, Babylon *.dict and Dict formats. GUI versions are available in the form of Qwordtrans (built with the Qt toolkit), Kwordtrans (for KDE 2) and Wordtrans-web, which uses a web browser as the interface. The first three of these also go by the names Wordtrans-console, Wordtrans-KDE and Wordtrans-Qt. Interfaces to the clipboard for automatic look-up.
GUI dictionary utility which supports fuzzy searches. Not to be confused with Kdict.
XQuick Translator (tested: demonstration version 1.2. alternative link here)
A commercial dictionary utility, currently priced at euro 12.95. Supplied with an (extensible) English/German dictionary with over 120,000 entries. A demonstration version is also available. Interfaces to the clipboard for automatic look-up.
Reviews, tips, resources
A very comprehensive list of dictionary utilities available for Linux which, at the time of writing, someone is still updating regularly.
Nice description, in German, of Xquick and Kquick, with useful tips.
Computing Services Information Document, Rutgers University, Camden (State University of New Jersey)
Useful information on using dict, xdict, and ispell from the command line.
Host to an open-source translation glossary for information technology.
An Internet-based dictionary project analogous to Wikipedia.
HyperDic English dictionary
Since HyperDic is a perfectly standard XHTML hypertext, it can be accessed from any browser, on all modern platforms (Windows, Macintosh, Unix/Linux), without any kind of program installation.
Encyclopédie Hachette 2007
Marco Amans reports that this French encyclopaedia will run on Linux.