Dictionaries on iOS 8 not working
You can re-enable the apple dictionary by following this steps:


Tap on the word you want to define to select it and activate the popup.
Tap on Define to call up the dictionary.
Tap on Manage.
Now activate/download the Apple Dictionary or any other dictionaries you want.
Tap the X button beside any extra dictionaries you want to remove.


Now you should have your dictionary enabled again.