cotangent

1 :  a trigonometric function that for an acute angle is the ratio between the leg adjacent to the angle when it is considered part of a right triangle and the leg opposite

2 :  a trigonometric function cot θ that is equal to the cosine divided by the sine for all real numbers θ for which the sine is not equal to zero and is exactly equal to the cotangent of an angle of measure θ in radians