To THROW your HEAD BACK is to quickly bend your head backwards, so your chin is raised and your neck is exposed. As if you are straining to see the top of a very high building or something. Along with the roar of heartless laughter, it shows that the blacksmith's attitude is scornful or contemptuous.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.