Ding is a dictionary lookup program for the X Window system on Linux/Unix. It comes with a German-English Dictionary with about 253,000 entries. It is based on Tk version >= 8.3 and uses the agrep or egrep tools for searching. In addition ding can also search in English dictionaries using dict(1) and check spelling using ispell(1). It has many configuration options, such as search preferences, interface language (English or German), and colors. It has history and help functions and comes with useful key and mouse bindings for quick and easy lookups.
Artha is a handy thesaurus based on WordNet with distinct features like global hot key look up, passive desktop notification, regular expression based search, etc. Artha may be used as a free open-source replacement/clone to the proprietary WordWeb Pro thesaurus (which is also based on WordNet) on Unix-like and Windows operating systems.
sdvplayer is a tool to help you improve your vocabulary in a foreign language by watching movies with subtitles in that language. It allows you to look up the meaning of a word displayed in the subtitles just by clicking on it. The meaning will be printed right on the screen and the player will be paused. Playing can be resumed just by pressing the space bar. It can play movies in many of the formats supported by libav*. Subrip (.srt), microDVD, and subviewer subtitle formats are supported. The meaning can be looked up through an external command. The built-in dictionary parser can parse the stardict dictionary format.
TAO Translator (formerly, The Advanced Online Translator) uses online translation services to provide translations. Currently supported services: Google Translate (supports translation, language detection, dictionary, and reverse translations for single words); Microsoft Translator, a.k.a. Bing Translator (supports translation only); Yandex.Translate (supports translation and language detection); and Yandex.Dictionaries (supports dictionary with synonyms and reverse translations). More services are possible in the future.