BIQUADRAT'IC, n. The same as biquadrate. BIQUADRAT'IC, a. Pertaining to the biquadratic or fourth power. Biquadratic equation, in algebra, is an equation raised to the fourth power, or where the unknown quantity of one of the terms has four dimensions. Biquadratic parabola, in geometry, is a curve line of the third order, having two infinite legs tending the same way. Biquadratic root of a number, is the square root of the square root of that number. Thus the square root of 9 is 3, which is the biquadratic root of 81.

Biquadratic Bi`quad*rat"ic, a. [Pref. bi- + quadratic: cf. F. biquadratique.] (Math.) Of or pertaining to the biquadrate, or fourth power. Biquadratic equation (Alg.), an equation of the fourth degree, or an equation in some term of which the unknown quantity is raised to the fourth power. Biquadratic root of a number, the square root of the square root of that number. Thus the square root of 81 is 9, and the square root of 9 is 3, which is the biquadratic root of 81. Hutton.