Definition
The upward angle of an airplane's wings when measured from a horizontal reference line at the wing root. It is the actual structural angle built into the wing, viewed from the front of the airplane.
Plain English
The amount the wings angle upward as you look at the airplane from straight ahead. It is the real, physical angle of the wings, not an effect created by something else.
Context Anchor
Seen in airplane stability and handling discussions, especially when explaining why an airplane tends to roll back toward level after being disturbed.
Derivation
From Greek 'di-' (two) and 'hedra' (seat or surface), meaning 'two surfaces meeting at an angle.' 'Geometric' is added to specify that this is the actual built-in shape of the wings, as opposed to a stability effect that only behaves like dihedral.
Why Pilots Care
It enhances the aircraft's natural tendency to return to wings-level flight after a roll disturbance.
Grounding Statement
If you stand in front of the airplane and the wingtips sit higher than the wing roots, you are seeing geometric dihedral.
Intuition Check
Geometric dihedral means the physical wing angle you can see. It does not mean every possible stability effect that makes an airplane roll back toward level.
Example Sentence 1
The Cessna 172's geometric dihedral is visible from the front, with each wing angled slightly upward from the fuselage.
Example Sentence 2
Designers increased the geometric dihedral to improve roll stability in the new trainer.