di·he·dral / dīˈhēdrəl/ • adj. having or contained by two plane faces: a dihedral angle.• n. an angle formed by two plane faces. ∎ Aeron. inclination of an aircraft's wing from the horizontal, esp. upward away from the fuselage. Compare with anhedral. ∎ Climbing a place where two planes of rock meet at an angle of between 60° and 120°.