iPhone 5 my 'define' word feature no longer an option. How can get it back

I've googled this numerous times and can't find anything. Last night I went to the Apple store to speak with a "Genius". 3 different employees told me they have never heard of this and recommended that I try "googling it". I figured I might be better off trying to solve this problem on my own...

Any help is greatly appreciated!

Also, i'm not looking for the temporary fix of changing to British English. I live in the USA, not in Britain.