A meta search term is a keyword placed inside the meta keywords tag — a hidden list in a page's HTML that once told search engines what the page targeted. Google stopped using it for ranking in 2009, and it offers no SEO value today.
On the early web, a site owner could drop a comma-separated list into the keywords tag and hope to signal relevance to crawlers. The idea collapsed fast because it was trivial to abuse: anyone could list dozens of unrelated or competitor terms no human would ever see. Search engines learned to read the visible page instead, where words carry accountability.
Google has stated plainly that it does not use the keywords meta tag for ranking, and Bing has described treating it more as a possible spam signal than a help. Filling it in wins nothing; over-stuffing it can, at best, be ignored. There is also a quiet privacy cost: whatever you list is visible to anyone who views your page source, so a page publicly declaring every term it chases simply hands its strategy to competitors.
For the tags that still matter, see meta tag, and avoid keyword stuffing anywhere on the visible page. Solid on-page SEO replaced this tag long ago.