Thesaurus

A thesaurus is a book that lists words grouped together according to similarity of meaning (containing synonyms and sometimes antonyms), in contrast to a dictionary, which contains definitions and pronunciations.

In Information Science, Library Science, and Information Technology, specialized thesauri are designed for information retrieval. They are a type of controlled vocabulary, for indexing or tagging purposes. If you want more information about term you can take a look at http://en.wikipedia.org/wiki/Thesaurus

OpenKM can working with thesaurus defined in .owl and .rdfs formats.