Ariana

This is a very simple plugin that adds a “robots” meta tag to the head of your site with “noindex” in it.
The effect of the noindex robots meta tag is that search engines will not index your pages and posts at all. 
This is a better solution then the wordpress default settings option, which tells search engines to not crawl the URLs in the robots.txt. Because Google (and other search engines) sometimes still index URLs they haven’t crawled, for which they determine relevancy based on anchor text of links which lead to the specific URL.

Simple Noindex

Samir Shah

This plugin will issue a HTTP <code>410</code> response to requests for articles that no longer exist on your blog. When you delete a post or page, it records the URL for that page and issues a <code>410</code> response when that URL is requested. You can also manually manage the list of obsolete URLs.
The <a href="http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.4.11" rel="nofollow ugc">HTTP Specification</a> defines the <code>410</code> response header for use when a resource has been permanently removed. It informs robots visiting your site that the requested content has gone, and that they should stop trying to access it.
If you come across any bugs or have suggestions, please use the plugin support forum. I can’t fix it if I don’t know it’s broken! Please check the <a href="https://wordpress.org/extend/plugins/wp-410/faq/" rel="ugc">FAQ</a> for common issues.

410 for WordPress

A plugin that sends HTTP 410 (Gone) responses to requests for articles that no longer exist on your blog.

Simple Noindex vs 410 for WordPress