Quadrille ruled graph paper, quad paper.

A square tiling of the plane.

(mathematics) The formula x=(-b±√)/(2a) for finding roots of the quadratic equation.

(mathematics) Any function whose value is the solution of a quadratic polynomial

A period of 4 years, particularly (historical) the sets of four years in the ancient Egyptian and Greek calendars.

plural of quadratic integer

(medicine) a heart disease in which there is an abnormally long delay between the electrical excitation (or depolarization) and relaxation (repolarization) of the ventricles of the heart.

(mathematics, dated) Initialism of quod erat demonstrandum (“what had to be proved; what was to be demonstrated”): placed at the end of a mathematical proof to show that the theorem under discussion is proved.

Some fact or scenario that proves an argument or proposition; a justification.

(China) An administrative subdivision of China roughly equivalent to districts, distinguished from the more rural "counties" (xian).