Here is Donald Zepp, former music shop owner, teacher and master banjoist on the terms "clawhammer" and "frailing":

"So what is the difference between "frailing" and "clawhammer?" Depending on your point of view, there either is none, or "clawhammer" describes a "double-thumb" technique while "frailing" precludes it unless otherwise noted. What is clear is that if one uses any of these terms in a restrictive sense, he should make that clear, for there are others who will interpret the term in its broadest sense."

Complete article here.

For my part, I think of any playing style where you form your hand in a claw and appear to be beating on your instrument with an invisible hammer to be "clawhammer". That should keep me out of trouble.