<p><strong>Noun</strong></p><ul><li>a quarter of a circle; an arc of 90°.</li><li>the area included between such an arc and two radii drawn one to each extremity.</li><li>something shaped like a quarter of a circle, as a part of a machine.</li><li>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.</li><li>an instrument, usually containing a graduated arc of 90°, used in astronomy, navigation, etc., for measuring altitudes.</li><li>Astrology: one of the four quarters of the horoscope: determined by the ascendant, nadir, descendant, and midheaven and numbered counterclockwise from the ascendant.</li><li>Furniture: one of two metal sliding pieces, of quadrant form, used to support the fall front of a desk from above.</li></ul>