Hello Leo -
When you say "dictionary" functionality, can you describe in more detail what you would like to see?
Pure vocabulary translation SHOULD be supported both by the actual Microsoft Translator API and the Java API as it is not required that the translation text be a full phrase. This can be accomplished simply by calling Translate.execute() passing only the single word you wish to translate as the first parameter. Microsoft's rate limits are applied on a per-character basis (as opposed to per-call, for example), so using it for single-word vocabulary translation should not be inherently any more expensive than full-phrase translations.
If you are referring to more robust dictionary functionality - with definitions, and pronunciation - as described
here and found on the Microsoft Translator
main page, then that type of functionality is not currently supported by the public Microsoft Translator API.
-jonathan