The angle between two intersecting planes. In a molecule with atoms A-B-C-D, the dihedral angle (A-B-C-D) is the angle between the planes defined by (A, B, C) and by (B, C, D). By convention, the angle is positive for a right-handed rotation from the first plane to the second, i.e., for a right-handed twist along the sequence A-B-C-D.

the angle between the two surfaces on either side of a crease, defined as the angle between the surface normals.

Umm... it's the angle of a wing. Kinda hard to explain. Easier to show it, so see Figure 2.

Angle between an atom and a plane (formed by three or more other atoms).

The angle defined by two given faces meeting at an edge, e.g., all the dihedral angles of a cube are 90 degrees. An almost-spherical polyhedron (with many faces) has small dihedral angles.

The angle that an aeroplane's wings make with a horizontal plane. A larger dihedral angle gives greater roll(lateral) stability at the cost of efficiency. If the wings angle upwards, it is called the dihedral angle. Downward angled wings are said to have an anhedral angle.

The upward angle of the wings that is formed where the wings connect to the fuselage.

the angle between groups attached on adjacent carbon atoms when viewed in a Newman projection.

An aeroplane is said to possess a dihedral angle when it wings rise upward from the centre of the machine