i saw this on one of the kindle screen savers. i didn't remember seeing it in the user guide, but sure enough it is in there. so just in case others missed it i'll post it here and ask a question: why isn't '@dict <xxxx>' one of the choices?
Tip: You can also search any of the remote locations directly by typing shortcuts into the Search line. The format for the shortcuts is to type the @ character followed by the remote destination and then the search term. For instance, to search the Kindle Store for trees, enter @store trees in the Search line. This will take you directly to the Kindle Store search results page for trees. Other shortcuts are @wiki and @web.