Biquadratic

[Sarah]

Of or pertaining to the biquadrate, or fourth power.Biquadratic equation (Alg.), an equation of the fourth degree, or anequation in some term of which the unknown quantity is raised to thefourth power.-- Biquadratic root of a number, the square root of the square rootof that number. Thus the square root of 81 is 9, and the square rootof 9 is 3, which is the biquadratic root of 81. Hutton.