plumb line, perpendicular -- (a cord from which a metal weight is suspended pointing directly to the earth's center of gravity; used to determine the vertical from a given point)
perpendicular -- (an extremely steep face)
Overview of adj perpendicular
The adj perpendicular has 3 senses
perpendicular -- (intersecting at or forming right angles; "the axes are perpendicular to each other")
vertical, perpendicular -- (at right angles to the plane of the horizon or a base line; "a vertical camera angle"; "the monument consists of two vertical pillars supporting a horizontal slab"; "measure the perpendicular height")
perpendicular -- (extremely steep; "the great perpendicular face of the cliff")