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: Webster's Revised Unabridged Dictionary (1913)