dihedral Syllabification: (di·he·dral)Pronunciation: /dīˈhēdrəl/Definition of dihedral adjective having or contained by two plane faces:a dihedral angle noun an angle formed by two plane faces. Aeronautics inclination of an aircraft’s wing from the horizontal, especially upward away from the fuselage. Compare with anhedral. North American Climbing a place where two planes of rock meet at an angle of between 60° and 120°. Origin: late 18th century: from di-1 'two' + -hedral (see -hedron)dihedral in other Oxford dictionaries Definition of dihedral in the British & World English dictionary