Thesaurus Desktop .NET is a Windows Forms control providing end users with thesaurus functionality and developers with a highly customizable, yet simple to work-with component. The thesaurus contains over 60,000 terms with synonyms, antonyms and related words.

Features
Dialog or context menu based integration
Rich design time support + some source code
Open API allows great flexibility
3rd Party control support
Thorough documentation and support

Only for V.I.P