S: (n) 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)
S: (adj) perpendicular (intersecting at or forming right angles) "the axes are perpendicular to each other"
S: (adj) 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"
S: (adj) perpendicular (so steep as to be nearly veritcal) "the great perpendicular face of the cliff"