Great question, Derek.
I would define a timber framer as "one who builds timber framed structures"
But for more specific meaning, I think it depends on which adjective you use.
Professional Timber Framer--a carpenter who earns their daily living practicing the trade of timber framing
Amateur Timber Framer--a person who is an enthusiast of the craft of timber framing and pursues it as a hobby
Itinerant Timber Framer--a professional timber framer who works independently on a
freelance basis
Soon to exist:
Guild Apprentice Timber Framer
Licensed Journeyworker Timber Framer
These definitions are, of course, my .02.
Anyone have any others to add?
Whit