[kwod-ruh-cher, -choor]
noun
1.
the act of squaring.
2.
Mathematics.
a.
the act or process of finding a square equal in area to a given surface, especially a surface bounded by a curve.
b.
the act or process of finding an area or calculating an integral, especially by numerical methods.
c.
a definite integral.
3.
Astronomy.
a.
the situation of two heavenly bodies when their longitudes differ by 90°.
b.
either of the two points in the orbit of a body, as the moon, midway between the syzygies.
c.
(of the moon) those points or moments at which a half moon is visible.
4.
Electronics. the relation between two signals having the same frequency that differ in phase by 90°.

Origin:

Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
Collins
World English Dictionary
 quadrature (ˈkwɒdrətʃə) —n 1. maths the process of determining a square having an area equal to that of a given figure or surface 2. the process of making square or dividing into squares 3. astronomy a configuration in which two celestial bodies, usually the sun and the moon or a planet, form an angle of 90° with a third body, usually the earth 4. electronics the relationship between two waves that are 90° out of phase

Collins English Dictionary - Complete & Unabridged 10th Edition
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American Heritage
Science Dictionary
 quadrature   (kwŏd'rə-chr')  Pronunciation Key  The process of constructing a square equal in area to a given surface. A configuration in which the position of one celestial body is 90° from another celestial body, as measured from a third. For example, the half moon lies in quadrature from the Sun when Earth is the reference point. See more at elongation.
The American Heritage® Science Dictionary
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Encyclopedia Britannica
Encyclopedia

in astronomy, that aspect of a heavenly body in which its direction as seen from the Earth makes a right angle with the direction of the Sun. The Moon at First or Last Quarter is said to be at east or west quadrature, respectively. A superior planet (outside the Earth's orbit) is at west quadrature when its position is 90 west of the Sun. It rises around midnight, reaches the meridian (a great circle on the celestial sphere, passing through the north and south poles and the zenith) near sunrise and sets near noon. At east quadrature the planet is near the meridian at sunset and sets near midnight. At both quadratures the planet is at gibbous phase (more than half but not all of the disk illuminated), but only Mars shows up conspicuously gibbous