dictionaryiosiphone
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
Yo ! Man, I got the best thing for you.
Just type some of your characters of word & press F5 & see the magic, It is what you want. Suppose your not getting the word rub some & get what you want.
Here is snap-shot of what you want. ( source of lots of shortcut keys )
Suppose, I am a user, I would do as follows.
simple & short just F5 does all for you, no need to press Cmd+: and then get correct one from list. It will give you list on the spot.
I would try the Dictionary.com app.
http://itunes.apple.com/WebObjects/MZStore.woa/wa/viewSoftware?id=308750436&mt=8
Best Answer
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.