I found this RFE, dated 2008 and approved, but I think it was never implemented (or if it was, I don't see an improvement):

http://www.webgui.org/rfe/request-for-enhancement/search-synopsis-default

In 7.7.33 stable the synopsis var in the search still defaults to displaying the title, menu title and url, which looks odd. Some search results from the default installation:

Tell A Friend
    Tell A Friend Tell A Friend tell a friend
Getting Started
    Getting Started Getting Started getting started
Site Map
    Site Map Site Map site map

The best way of fixing this would be to let an empty synopsis be an empty synopsis, so we can test against it in the template:

<tmpl_if synopsis>
  <tmpl_var synopsis>...
</tmpl_if>

With an "else" statement, it would still be possible to add an alternative text if the synopsis is empty.

Thanks,

Rogier