Source : Webster's Revised Unabridged Dictionary (1913)

Bow-compass \Bow"-com`pass\, n.; pl. {Bow-compasses}.
   1. An arcograph.

   2. A small pair of compasses, one leg of which carries a
      pencil, or a pen, for drawing circles. Its legs are often
      connected by a bow-shaped spring, instead of by a joint.

   3. A pair of compasses, with a bow or arched plate riveted to
      one of the legs, and passing through the other.