perpendicular

Etymology

From Middle French perpendiculaire, from Old French perpendiculer, from Latin perpendiculum (“plumb line”).

adj

1. (geometry) At or forming a right angle (to something).
   In most houses, the walls are perpendicular to the floor.
   A doorknob of whatever roundish shape is effectively a continuum of levers, with the axis of the latching mechanism—known as the spindle—being the fulcrum about which the turning takes place. Applying a force tangential to the knob is essentially equivalent to applying one perpendicular to a radial line defining the lever. 2012-03, Henry Petroski, “Opening Doors”, in American Scientist, volume 100, number 2, pages 112–3
2. Exactly upright; extending in a straight line toward the centre of the earth, etc.
3. Independent of or irrelevant to each other; orthogonal.
   Hey, I'm not unsabotaging anything! This is completely perpendicular sabotage! May 31 2019, David M. Willis, “Wrangled”, in Dumbing of Age

noun

1. (geometry) A line or plane that is perpendicular to another.
2. A device such as a plumb line that is used in making or marking a perpendicular line.
3. (obsolete, slang) A meal eaten at a tavern bar while standing up.