From the press release:
At The Wall Street Journal's D8: All Things Digital Conference, a gathering of influential leaders in media and technology, Wordnik, a company creating new ways to unlock the value of digital content, will demonstrate today how media and publishing leaders can enhance discovery and bring new opportunities for monetization inside the ereader platform. The company will also announce a dozen media and publishing partners.
New partners joining the original eight Smartwords partners (Forbes; Huffington Post; Ibis Reader; Internet Archive; The New York Times; O'Reilly Media; Scribd; and Vook) are: Audio Newspaper; Audiovox; Baen Books; IDG; IGN; MetroLeap; NPR; Scientific American; Simon & Schuster; Six Apart; and Ziff Davis.
That's a pretty impressive set of business partners.
Basically this is a crowd sourced dictionary that pulls definitions from a bunch of existing dictionaries as well as from all over the web. Their website is boasting 9m words catalogued. If that's true then this could be the biggest dictionary in the world.
I've played with the site for a while. It's off to a good start, but they made at least one basic mistake in their search algorithm. It can't find compound words like "self sealing stem bolts". I'm sure they'll fix this soon, though.