Not a request I get often but there can be many reasons why you might want Google to ignore a website. One reason can be that a site is in a development stage and you may not want the content indexed by Google so it does not show up in a Google (or other search engine) search.
There is a file called robots.txt on everyones web server that can contain instructions to tell search engines to ignore your site but this can be difficult to access unless you are techie. For WordPress users there is a much simpler solution as there is a setting available to tell search engines to ignore your site.
The position of this setting has changed over the versions but in the latest version, WordPress 4.0, you can find the setting in Settings>> Reading >> Search engine visibilty (see screenshot below)
Once you untick this setting then normal, search engine service, will resume.