Dihedral /(?)/

Di·he·dral

Dihedral

a.
  1. Having two plane faces; as, the dihedral summit of a crystal.
  2. Of a kite or an aëroplane, having wings that make with one another a dihedral angle, esp. when the angle between the upper sides is less than 180°.
  3. Of wing pairs, inclined at an upward angle to each other. (Aëronautics)

Phrases & Compounds
Dihedral angle
the angular space contained between planes which intersect. It is measured by the angle made by any two lines at right angles to the two planes.