User-defined synonym sets.

The UserThesaurusFile is the name of an XML file. To create the file, start dtSearch Desktop, click Options > Preferences > User Thesaurus and use the dialog box to set up the synonym definitions. The XML file will be saved as thesaur.xml in your dtSearch UserData folder. See User Thesaurus in the dtSearch Desktop help for information on this setting. 

The XML contents of a thesaurus file can also be provided directly in the UserThesaurusFile string.