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Adjective: dihedral  dI'hee-drul
  1. Having two plane faces
    "the dihedral summit of a crystal"
  2. Of a kite or an aeroplane, 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

Encyclopedia: Dihedral