quadrant Meaning, Definition & Usage

  1. noun a quarter of the circumference of a circle
    quarter-circle.
  2. noun any of the four areas into which a plane is divided by two orthogonal coordinate axes
  3. noun the area enclosed by two perpendicular radii of a circle
  4. noun a measuring instrument for measuring altitude of heavenly bodies

WordNet

Quad"rant noun
Etymology
L. quadrans, -antis, a fourth part, a fourth of a whole, fr. quattuor four: cf. F. quadrant, cadran. See Four, and cf. Cadrans.
Definitions
  1. The fourth part; the quarter. Obs. Sir T. Browne.
  2. (Geom.) The quarter of a circle, or of the circumference of a circle, an arc of 90°, or one subtending a right angle at the center.
  3. (Anal. (Geom.) One of the four parts into which a plane is divided by the coördinate axes. The upper right-hand part is the first quadrant; the upper left-hand part the second; the lower left-hand part the third; and the lower right-hand part the fourth quadrant.
  4. An instrument for measuring altitudes, variously constructed and mounted for different specific uses in astronomy, surveying, gunnery, etc., consisting commonly of a graduated arc of 90°, with an index or vernier, and either plain or telescopic sights, and usually having a plumb line or spirit level for fixing the vertical or horizontal direction.

Webster 1913