radgh

This simple and lightweight plugin adds a “Hide from search engines” checkbox above the publish box to pages. By 
ticking this box, a meta tag will be placed into the <code><head></code> section of your page specifying that robots should 
not index the page.
By default this only applies to pages. You may extend this functionality to posts or other custom post types with a small bit of code. See the FAQ’s tab for further instructions.

Noindex Pages

Ask search engines not to index individual pages by checking an option in the publish post box.

room34

This plugin is an add-on for Modern Tribe’s The Events Calendar plugin. It adds a “noindex” meta tag to the individual detail pages for events after their end date has passed, to prevent them from appearing in search engines like Google or Bing.
Note that this only takes effect the next time a search engine indexes your site, so past events may still appear in search results for a few days.

noindex Past Events for The Events Calendar

Automatically add a "noindex" meta tag to The Events Calendar's detail pages for past events, to prevent them from appearing in search engines.

Noindex Pages vs noindex Past Events for The Events Calendar