Definition of "Perpendicular" :

noun: an extremely steep face

noun: 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

noun: a Gothic style in 14th and 15th century England; characterized by vertical lines and a four-centered (Tudor) arch and fan vaulting

noun: a straight line at right angles to another line

adjective: so steep as to be nearly veritcal

"The great perpendicular face of the cliff."

adjective: at right angles to the plane of the horizon or a base line

"Measure the perpendicular height."

adjective: intersecting at or forming right angles

"The axes are perpendicular to each other."