Definition of: perpendicular

(pûr′pən·dik′yə·lər) adjective
1. Being at right angles to the plane of the horizon; upright or vertical.
2. Math. Meeting a given line or plane at right angles. See synonyms under RIGHT.
—noun
1. A perpendicular line.
2. An appliance or instrument used to indicate the vertical line from any point; a plumb rule.
3. A line at right angles to another line or to a plane.
4. A vertical line or vertical face; loosely, any steep incline or face.
5. Perpendicular position.
6. Moral uprightness. [<OF perpendiculer <L perpendicularis <perpendiculum a plumb line <per- thoroughly + pendere hang]
—per′·pen·dic′u·lar′i·ty (-lar′ə·tē) noun
—per′pen·dic′u·lar·ly adverb