A barrel which is fashioned by hammering 2 strips of metal together around a mandrel. They were expensive when they were in vogue 125 years ago but they are weak and unwanted now.
A damascus barrel is a barrel made of damascus steel, which is steel produced by hammering two different steels together. The twist refers to the pieces of steel being twisted while they are...
Quite often the shotgun will tell you how the barrels are made. If it says "twist" or "laminated" or "damascus", then it is one of the types generally called damascus. If it says "armory", "forged",...