Plain English Meaning
How well an airplane rights itself when one wing drops. If a gust lifts the right wing, a laterally stable airplane will tend to roll back to wings-level on its own.
Full Definition
The tendency of an airplane to return to wings-level flight after being disturbed in roll about its longitudinal axis. It is one of the three axes of stability and is achieved primarily through wing dihedral, sweepback, keel effect, and weight distribution.
Context Anchor
Seen when studying turns, bank control, gust recovery, and how an airplane behaves if it is disturbed from wings-level flight.