Definition of cosecant
1
: a trigonometric function that for an acute angle is the ratio between the hypotenuse of a right triangle of which the angle is considered part and the leg opposite the angle
2
: a trigonometric function csc θ that is the reciprocal of the sine for all real numbers θ for which the sine is not zero and that is exactly equal to the cosecant of an angle of measure θ in radians
