Blocking URL keywords

First of all, thank you for this great tool.  I really do appreciate it!

My question is this:  Is there a way that websites with certain keywords in the URL can be blocked without having to be on the blacklist?  There are a few terms that only show up in adult site URLs that do not show up in safe site URLs.  I know there is the chance that some safe sites might be inadvertently blocked, but those can be manually whitelisted as people find them.

Thanks!