perpendicular

adj

1. 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.”

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!”

4. Of a style of English Gothic architecture from the fourteenth and fifteenth centuries, marked by stiff and rectilinear lines, mostly vertical window-tracery, depressed or four-centre arch, fan-tracery vaulting, and panelled walls.

noun

1. 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.