1. (a.) Of or pertaining to the biquadrate, or fourth power.

2. (n.) A biquadrate.

3. (n.) A biquadratic equation.

aboveboard authentic biquadratic bona fide cube-shaped cubed cubic cubiform cuboid diced fair and square four four-legged four-rayed genuine good-faith oblong on the level on the square on the up-and-up open open and aboveboard orthogonal quadrangular quadrate quadratic quadric quadriform quadrilateral quadrinomial quadrivalent quadruped quartic quartile quaternary rectangular rhombic rhomboid single-hearted square square-dealing square-shooting straight straight-shooting tetractinal tetrad tetragonal tetrahedral tetravalent trapezohedral trapezoid up-and-up veritable