From HomoExcelsior

1. A circular arc of 90; one fourth of the circumference of a circle. 2. The plane area bounded by such an arc and two perpendicular radii. 3.  counting counterclockwise from the area in which both coordinates are positive. 4. A machine part or other mechanical device that is shaped like a quarter circle. 5. An early instrument for measuring altitude of celestial bodies, consisting of a 90 graduated arc with a movable radius for measuring angles.

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