What is the meaning of Dihedral?

An angle between two plane surfaces

The upward slope of an aircraft's wing

The angle between pairs of chemical bonds separated by a third bond

Consisting of, relating to or contained between two plane surfaces.

Having wings that form a dihedral angle, especially when the angle between the upper sides is less than 180°.

Of wing pairs, inclined at an upward angle to each other.

Source: wiktionary.org