\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.