n. Math. 1 the trigonometric function that is equal to the ratio of the side opposite a given angle (in a right-angled triangle) to the hypotenuse. 2 a function of the line drawn from one end of an arc perpendicularly to the radius through the other. sine curve (or wave) a curve representing periodic oscillations of constant amplitude as given by a sine function: also called SINUSOID.
[ L sinus curve, fold of a toga, used in med.L as transl. of Arab. jayb bosom, sine ]