Don't cite Google as a dictionary.
Google has licensed two of the dictionaries from Oxford Dictionaries for their search product:
- The Oxford Dictionary of English
- The New Oxford American Dictionary
These aren't bad dictionaries, mind you. The ODE is a large single-volume dictionary which gives very good coverage of Present-Day English, including many examples taken from the corpus Oxford used to assemble the dictionary. The NOAD is a version of this dictionary, not quite as good, which focuses on American English. The ODE and NOAD are not called by these names online; instead, they've been rebranded as Oxford Dictionaries, or Oxford Living Dictionaries.
Whatever you call them, it's confusing. The OED is a very different dictionary – a large multi-volume historical dictionary, not specifically focused on Present-Day English – but the acronym is very similar to ODE, so they're easily confused. And the "Oxford Dictionaries" name is likewise confusing, as the OED is the most well-known Oxford dictionary, but it isn't available at the Oxford Dictionaries website.
So it's a bit of a mess. But referring to these as the "Google dictionary" just adds to the confusion. Although Google has the license to present these search results without attribution, they haven't compiled their own dictionaries, and if you don't name the actual source, it's difficult for people to learn about the dictionaries themselves – their advantages and disadvantages, how they were compiled, what their purpose and coverage is, and so forth.
What's worse, Google doesn't return these results to all users. Many users on this site use Google in languages other than English, but the English dictionary results are not shown to all of these users. If someone cites the "Google dictionary" with a link to a Google search, the link simply won't work for many of the users on this site. That means the link is not a proper citation, and it should not be used on this site.
Even worse, imagine Google licensing another dictionary in the future. Apple did this with the Japanese language dictionaries included with its operating system a few years back, dumping one set of dictionaries and replacing them with another when it made financial sense to do so. Since Google doesn't name their sources, you can imagine this could turn out to be terribly confusing!
Linking to a Google search is just a bad idea. If you want to link to the ODE or NOAD, please link directly to the Oxford Dictionaries website.