Definition
The angle, measured in degrees, between the aircraft's lateral axis (wingtip to wingtip) and the horizon when the aircraft is rolled to one side. It describes how steeply the wings are tilted during a turn.
Plain English
How far the wings are tilted away from level. A small tilt is a shallow turn; a larger tilt is a steeper turn.
Context Anchor
You will see this term when learning turns, judging aircraft attitude, and discussing how steeply an airplane is banking.
Derivation
Bank' comes from old nautical and later aviation use, where it described leaning a vessel or aircraft to one side. Pairing it with 'angle' simply puts a number on how far the aircraft is leaned over.
Why Pilots Care
Bank angle directly sets the turn rate and raises the load factor the wings must support.
Intuition Check
Bank does not mean money or the side of a river here. In flying, it means the airplane is tilted left or right, and the angle of bank is how much it is tilted.
Example Sentence 1
The instructor asked the student to roll into a 30-degree angle of bank and hold it through a full 360-degree turn.
Example Sentence 2
A steeper angle of bank shortens the turn radius but increases the load factor felt in the seat.