Visuwords is an online dictionary and thesaurus that helps you find word meanings and explore the association between different words.
When you search a word, all the associated words get displayed as nodes joined together to form a a network.
Hover over nodes to see the definition of the associated word or double-click to further expand the tree. You can grab any node and pull it away from the others to clarify connections.
Best of all, you can download Visuwords for free and use it on your server or intranet.