Type in a word and a dictionary definition on top of the search results or adjacent to it. I love this feature because it kills all those spammy dictionary websites like, Mirriam-Webster (that's right you two. I said it. You are spammy).
Why don't we all just give up and let Google do everything for us:
Because, you know Google is making it almost impossible for you to really search for stuff anymore. It is just giving you the best guess it has of what you want and telling you to avoid all the other crap because it is algorithmically wrong.
Works great for very specific facts like what is the meaning of the word antediluvian.
It's useless when you are looking for the definitive authority of Klingon.
On the other hand, this new search feature does a great job of shaming you into rethinking your word choices because, the last time mendacious peaked in literature was the late 19th Century.
So, suck it Charles Dickens, and Emily Bronte. You have no SEO game you dead writers, you.
Seriously, though, the addition of Ngram Views of word usage is a really fun thing that you know will get killed by Larry Page at some point because it is too academic and too fun and not likely to buy anyone a new plane.