Source : Webster's Revised Unabridged Dictionary (1913)

Quadratic \Quad*rat"ic\, a. [Cf. F. quadratique.]
   1. Of or pertaining to a square, or to squares; resembling a
      quadrate, or square; square.

   2. (Crystallog.) Tetragonal.

   3. (Alg.) Pertaining to terms of the second degree; as, a
      quadratic equation, in which the highest power of the
      unknown quantity is a square.

Source : WordNet®

quadratic
     adj 1: of or relating to or resembling a square; "quadratic shapes"
     2: of or relating to the second power; "quadratic equation"

quadratic
     n 1: an equation in which the highest power of an unknown
          quantity is a square [syn: {quadratic equation}]
     2: a polynomial of the second degree [syn: {quadratic
        polynomial}]