Circumferentor
Pronunciation : Cir*cum`fer*en"tor
Part of Speech : n.
Etymology : [See Circumfer.]
Definition : 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?, 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.
Source : Webster's Unabridged Dictionary, 1913