a quarter of a circle; an arc of 90°.
the area included between such an arc and two radii drawn one to each extremity.
something shaped like a quarter of a circle, as a part of a machine.
Geometry, Astronomy one of the four parts into which a plane, as the face of a heavenly body, is divided by two perpendicular lines, numbered counterclockwise from upper right: the first quadrant of the moon.
an instrument, usually containing a graduated arc of 90°, used in astronomy, navigation, etc., for measuring altitudes.