perpendicular

adjective

• 1at an angle of 90° to a given line, plane, or surface:dormers and gables that extend perpendicular to the main roofline
• at an angle of 90° to the ground; vertical:the perpendicular cliff
• (of something with a slope) so steep as to be almost vertical:guest houses seem to cling by faith to the perpendicular hillside

• 2 (Perpendicular) denoting the latest stage of English Gothic church architecture, prevalent from the late 14th to mid 16th centuries and characterized by broad arches, elaborate fan vaulting, and large windows with vertical tracery:the handsome Perpendicular church of St. Andrew

noun

• a straight line at an angle of 90° to a given line, plane, or surface:at each division, draw a perpendicular representing the surface line
• (usually the perpendicular) perpendicular position or direction:the wall declines from the perpendicular a little inward
• an instrument for indicating the vertical line from any point, as a spirit level or plumb line.