adj. & n.
adj. 1 a at right angles to the plane of the horizon. b (usu. foll. by to) Geom. at right angles (to a given line, plane, or surface). 2 upright, vertical. 3 (of a slope etc.) very steep. 4 (Perpendicular) Archit. of the third stage of English Gothic (15th-16th c.) with vertical tracery in large windows. 5 joc. in a standing position.
n. 1 a perpendicular line. 2 a plumb-rule or a similar instrument. 3 (prec. by the) a perpendicular line or direction (is out of the perpendicular). perpendicularity n. perpendicularly adv.
[ ME f. L perpendicularis f. perpendiculum plumb-line f. PER- + pendere hang ]