perpendicular

/ˌˈpʌrpənˌdɪkjələr/

/pəpɪnˈdɪkjulə/

Other forms: perpendiculars

Two lines that form a T are perpendicular to each other. They meet at a right angle. A person who is standing is perpendicular to the earth.

Use perpendicular to describe lines, angles, and direction. In geometry a perpendicular angle is 90 degrees, a perfect L. On a compass, East and North are perpendicular to each other. The term can be used more generally to describe any steep angle. You might talk about a ski slope that is nearly perpendicular but that's impossible since gravity would make you fall off a 90-degree angle. But if it's close enough, no one's really measuring.

Definitions of perpendicular

1. adjective

   intersecting at or forming right angles
   “the axes are perpendicular to each other”

   synonyms:

   normal

   forming a right angle

   orthogonal, rectangular

   having a set of mutually perpendicular axes; meeting at right angles

   right

   having the axis perpendicular to the base

   antonyms:

   parallel

   being everywhere equidistant and not intersecting

   oblique

   slanting or inclined in direction or course or position--neither parallel nor perpendicular nor right-angled

   comparable

   able to be compared or worthy of comparison

   convergent

   tending to come together from different directions

   divergent, diverging

   tending to move apart in different directions

   inclined

   at an angle to the horizontal or vertical position

   antiparallel

   (especially of vectors) parallel but oppositely directed

   collateral

   situated or running side by side

   nonconvergent, nonintersecting

   (of lines, planes, or surfaces) never meeting or crossing

   bias

   slanting diagonally across the grain of a fabric

   cata-cornered, catacorner, cater-cornered, catercorner, catty-corner, catty-cornered, kitty-corner, kitty-cornered

   slanted across a polygon on a diagonal line

   crabwise, sideways

   (of movement) at an angle

   diagonal

   connecting two nonadjacent corners of a plane figure or any two corners of a solid that are not in the same face

   nonparallel

   (of e.g. lines or paths) not parallel; converging

   oblique-angled

   having oblique angles

   symmetric, symmetrical

   having similarity in size, shape, and relative position of corresponding parts
2. adjective

   at right angles to the plane of the horizon or a base line
   “measure the perpendicular height”

   synonyms: vertical

   steep

   having a sharp inclination

   plumb

   exactly vertical

   upended

   turned up on end

   unsloped, upright

   in a vertical position; not sloping

   straight

   having no deviations
3. adjective

   extremely steep
   “the great perpendicular face of the cliff”

   synonyms:

   steep

   having a sharp inclination
4. noun

   a straight line at right angles to another line
   type of:

   straight line

   a line traced by a point traveling in a constant direction; a line of zero curvature
5. noun

   a cord from which a metal weight is suspended pointing directly to the earth's center of gravity; used to determine the vertical from a given point
   synonyms: plumb line

   types:

   lead line, sounding line

   (nautical) plumb line for determining depth

   plumb rule

   a plumb line attached to a narrow board

   type of:

   cord

   a line made of twisted fibers or threads
6. noun

   an extremely steep face
   type of:

   face

   a vertical surface of a building or cliff
7. noun

   a Gothic style in 14th and 15th century England; characterized by vertical lines and a four-centered (Tudor) arch and fan vaulting
   synonyms: English-Gothic, English-Gothic architecture, perpendicular style

   types:

   Tudor architecture

   a style of English-Gothic architecture popular during the Tudor period; characterized by half-timbered houses

   type of:

   Gothic, Gothic architecture

   a style of architecture developed in northern France that spread throughout Europe between the 12th and 16th centuries; characterized by slender vertical piers and counterbalancing buttresses and by vaulting and pointed arches