So I was replying to a post here, when I accidentally double clicked a word in the persons reply. I got the normal "cut,copy,paste" menu but there was also an arrow. I was curious so I clicked the arrow, and lo and behold there was a built in dictionary! Don't know how known this feature is, but I want to commend apple for such an insanely useful feature. I can see how this would be a prime feature for people who don't/can't use their phones in their native language and their English isn't the greatest. I don't know why this isn't advertised.