A snippet is a text excerpt that appears below a page's title in our search results and describes the content of the page. Instant Previews are page snapshots that allow users to get a glimpse of the layout of the web pages behind each search result, in order to select the best result(s).
Snippets and Instant Preview are extremely useful to users and can help them decide whether or not to click on your site in the search results. You can, however, specify that Google should not show a snippet (in which case neither the text snippet nor the preview icon will appear).
To prevent Google from displaying snippets and Instant Preview for your page, place this tag in the <HEAD> section of your page:
<meta name="googlebot" content="nosnippet">
Note that this tag will prevent previews from appearing in regular search results, but will not affect previews on ads.
If you want your page to have a snippet in our search results, but want to prevent Google from using description information from the Open Directory Project, you can use the robots meta tag.