CIRCUMFERENTOR, noun An instrument used by surveyors for taking angles. It consists of a brass index, and circle, all of a piece; on the circle is a chart, divided into 360 degrees. There are also two sights to screw on and slide up and down the index; also a spangle and socket screwed on the back side of the circle to put the head of the staff in.
Source: Webster's 1828 American Dictionary ↗ · public-domain · returned verbatim, no AI