Changing the default iOS dictionary from New Oxford American Dictionary(NOAD) to Oxford English Dictionary(OED)? Anywhere in  the iPhone when you select a word the Define option pops up from the popup menu. Clicking on it brings up the definition for that word. The default dictionary it uses is the New Oxford American Dictionary(NOAD). I wonder if it can be changed to the Oxford English Dictionary(OED).



Image source: osxdaily.com
It looks like this is possible in iOS 7. When you click to define a word, in the bottom left there is a "Manage" button. Here, you can tap the X for a dictionary that you want to delete from your device and tap the cloud button to download a dictionary you want. So in your case, tap the X to delete the NOAD from your iPhone, and tap the cloud to download the OED to your iPhone.