MS Word 2007 (and I assume 2010) provides a useful option to "Look Up" a word or phrase, by right clicking and selecting Look Up. 

It then provides a list of sources, including Bing, but not including Google.
In "Research Options", there is an "Add Services" function, but entering either Google.co.uk or Google,com returns the message: "No services were added because the service provider did not provide any valid information". .

I don't suppose there's any chance of Google offering this useful service....