Dihedral

Webster's Dictionary of the English Language

·adj Having two plane faces; as, the dihedral summit of a crystal.

II. Dihedral ·add. ·adj Of wing pairs, inclined at an upward angle to each other.

III. Dihedral ·add. ·adj 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°.