Audax rides

What constitutes an "audaxy" frame?

I'm lazily looking around for one but the boundaries seem a bit blurred.

As far as I can tell it's:

• Mudguard clearances
  
• "Slightly more relaxed that a road frame" geometry (I have no idea what this means)
  
• Often made of steel (for comfort) but sometimes carbon
  
• Mounts for racks and bottles
  
• Not as long wheelbase as a tourer