Noun
slant height (plural slant heights)
The distance from any point on the circle of a right circular cone to its apex.
Mathematical pyramids and triangles A pyramid in which the apothem (slant height along the bisector of a face) is equal to times the semi-base (half the base width) is sometimes called a golden pyramid. Source: Internet
That can also be rewritten as or where r is the radius and l is the slant height of the cone. Source: Internet