If you frequently use OS X Dictionary app, and you love seeing antonyms, synonyms, and similar word suggestions inline, then you’ll want to download and install Terminology for OS X Dictionary. I’ve used it less than a day and already found it infinitely more useful than the standard dictionaries.
Terminology for iOS is based on WordNet, a great semantic lexical reference. We do not offer a full Mac app for Terminology, but have prepared a dictionary using this same great data for use in the built-in OS X Dictionary app.Terminology for OS X is not an app, and does not have some of the features of the iOS version. It is, however, a great resource and the integration with the OS X Dictionary makes it work great with contextual “Look up…” commands and other integrations provided by the Dictionary app.