Plain English Meaning
An airplane that is built strong enough and certified to safely perform maneuvers like loops, rolls, spins, and steep dives. Most everyday training airplanes are not in this category.
Full Definition
An airplane that has been designed, built, and certificated to withstand the structural loads and flight attitudes encountered during aerobatic maneuvers, including intentional flight involving abrupt changes in attitude, abnormal attitudes, or abnormal accelerations beyond those normal to typical flight.
Context Anchor
Seen in upset prevention and recovery training, where some practice maneuvers may require an airplane approved for aerobatic flight.