Source : Webster's Revised Unabridged Dictionary (1913)

Quadrature \Quad"ra*ture\, n. [L. quadratura: cf. F. quadrature.
   See {Quadrate}, a.]
   1. (Math.) The act of squaring; the finding of a square
      having the same area as some given curvilinear figure; as,
      the quadrature of a circle; the operation of finding an
      expression for the area of a figure bounded wholly or in
      part by a curved line, as by a curve, two ordinates, and
      the axis of abscissas.

   2. A quadrate; a square. --Milton.

   3. (Integral Calculus) The integral used in obtaining the
      area bounded by a curve; hence, the definite integral of
      the product of any function of one variable into the
      differential of that variable.

   4. (Astron.) The position of one heavenly body in respect to
      another when distant from it 90[deg], or a quarter of a
      circle, as the moon when at an equal distance from the
      points of conjunction and opposition.

   {Quadrature of the moon} (Astron.), the position of the moon
      when one half of the disk is illuminated.

   {Quadrature of an orbit} (Astron.), a point in an orbit which
      is at either extremity of the latus rectum drawn through
      the empty focus of the orbit.

Source : WordNet®

quadrature
     n : the construction of a square having the same area as some
         other figure