(US, Canada) an intersection with a circular shape and, usually, a central island

(netball) One of two semicircles in the goal thirds, radius 4.9 metres, in which the goal shooter and goal attack can shoot.

(mathematics) The problem, proposed by ancient Greek geometers, of using a finite ruler-and-compass construction to make a square with the same area as a given circle.

a circle formed by a plane that cuts a sphere not through its centre

Instrument for measuring azimuths. It is a graduated circle on a sight, gun carriage, searchlight, etc.

(geometry) A circle of radius 1. / (trigonometry, the unit circle) The circle of radius 1 with centre at the origin, used in defining trigonometric functions.

(baseball) The circle drawn or painted on the field where the next batter to hit waits.

(geography) The line which marks approximately the northernmost place in the Southern Hemisphere where the sun does not set on the summer solstice and does not rise on the winter solstice.

(philately) A cancellation mark consisting of an outer ring of concentric circles, cropped into a square shape.

(sports, boxing, wrestling, professional wrestling) The boxing or wrestling ring.