description of papers that have not been submitted to a venue? I have some published papers and in my CV, I mention them under the heading of "Publications".

However, I have some papers that I have not yet submitted to a venue (conference or journal). I think that I cannot mention these papers as "Publications". 

What is the best and more appropriate description for the papers that have not been submitted yet? e.g. "Research Papers"? Or "Research Manuscripts"? Or something else?
Work in Progress might be good as it implies that there may still be some work to do in the writing - and even some uncertainty about the final title. In addition it also subtly says that you are still active and not resting on your old achievements. 

You could, in addition, mark each paper according to its readiness, or at least those that are ready for submission. 

I think that Research Papers carries a connotation that they are internal and may not be published.