Source : Webster's Revised Unabridged Dictionary (1913)

Circumferentor \Cir*cum`fer*en"tor\, n. [See {Circumfer}.]
   1. A surveying instrument, for taking horizontal angles and
      bearings; a surveyor's compass. It consists of a compass
      whose needle plays over a circle graduated to 360[deg],
      and of a horizontal brass bar at the ends of which are
      standards with narrow slits for sighting, supported on a
      tripod by a ball and socket joint.

   2. A graduated wheel for measuring tires; a tire circle.