Menashe Avramov on Google+ first reported about the new “nositelinkssearchbox” meta tag. The use of this meta tag is “When users search for your site, Google Search results sometimes display a search box specific to your site, along with other direct links to your site. This meta tag tells Google not to show the sitelinks search box. “
Previously, Google announced search box to be appear in search.
Here is, how to use this new meta tag in head section of your page:
<meta name=”google” content=”nositelinkssearchbox” />
Read here, for all meta tags which are officially worked according to Google Guidelines.