Geometry . an intersecting line, esp. one intersecting a curve at two or more points.

Trigonometry .

(in a right triangle) the ratio of the hypotenuse to the side adjacent to a given angle.

(originally) a line from the center of a circle through one extremity of an arc to the tangent from the other extremity.

the ratio of the length of this line to that of the radius of the circle; the reciprocal of the cosine of a given angle or arc. Abbreviation

sec

cutting or intersecting, as one line or surface in relation to another.