Plain English Meaning
In a steep turn, the airplane wants to keep tipping further over on its own. The pilot has to actively hold the wings where they want them, often using a small amount of opposite aileron to stop the bank from increasing.
Full Definition
The tendency of an airplane in a steep turn to continue rolling into a steeper bank without further aileron input from the pilot. It occurs because the outside wing, traveling on a larger radius, moves faster through the air and produces more lift than the inside wing, which rolls the airplane further into the turn.
Context Anchor
Encountered during level turns, especially when learning steep turns and trying to hold a .