biquadratic : Idioms & Phrases

• noun an equation of the fourth degree
  biquadratic.
  

WordNet

• (Alg.), an equation of the fourth degree, or an equation in some term of which the unknown quantity is raised to the fourth power.

Webster 1913

• noun a polynomial of the fourth degree
  biquadratic; quartic polynomial.
  

WordNet

• 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.

Webster 1913