Thesaurus
The Moby Thesaurus II contains 30,260 root words, with 2,520,264 synonyms and related terms - an average of 83.3 per root word. Each line consists of a list of comma-separated values, with the first term being the root word, and all following words being related terms.
Grady Ward placed this thesaurus in the public domain in 1996. It is also available as a Debian package.
Read more about this topic: Moby Project