IOS 9.3.3 - 9.3.4, no dictionaries
I had the same issue, to fix it go to this directory in your device: /var/MobileAsset/Assets. 

There is a folder (com_apple_MobileAsset_DictionaryServices_dictionary2). Just replace the content of the folder from another apple device that has a working in-built dictionary.
Make sure the other device has the same iOS version as your device. 
Of course, you need to jailbreak both devices in order to get root access to extract and replace the folder.
That, or update to iOS 10 beta.

Hope that helps.