Biquadratic

a. [Lat. bis, twice, and Eng. quadratic; Fr. biquadratique.] Pertaining to the biquadratic, or fourth power.

Biquadratic equation (Alg.), an equation of the fourth degree, or one in which the unknown quantity is raised to the fourth power. Davies.—Biquadratic parabola (Geom.), a curve line of the third order, having two infinite legs tending the same way. Hutton.—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.