1 : so steep as to be nearly veritcal; "the great perpendicular face of the cliff"
nom
1 : 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
2 : a Gothic style in 14th and 15th century England; characterized by vertical lines and a four-centered (Tudor) arch and fan vaulting
adjectif
1 : intersecting at or forming right angles
2 : at right angles to the plane of the horizon or a base line