What is the term for the published altitude representing the maximum usable altitude for an airspace structure or route segment?

The term for the published altitude representing the maximum usable altitude for an airspace structure or route segment is indeed "Maximum Authorized Altitude" (MAA). This altitude is critical in ensuring safe separation between aircraft and obstacles, as well as providing adequate vertical clearance above terrain or other obstructions.

The MAA is specifically designed to prevent aircraft from exceeding operational limits, ensuring there is a safe buffer below the maximum altitude that can be safely utilized. When flying at or below the MAA, pilots can be assured that they are operating within defined safety parameters and that air traffic control can manage airspace effectively.

In comparison, Minimum Reception Altitude (MRA) refers to the lowest altitude that provides acceptable navigational signal reception. Minimum Crossing Altitude (MCA) indicates the lowest altitude at which an aircraft must cross specified waypoints. Off Route Obstruction Clearance Altitude (OROCA) provides a vertical clearance above terrain and obstacles for aircraft navigating off established routes. While these altitudes serve different purposes, the MAA specifically defines the upper limit for operational altitude in given airspace, making it the correct answer to the question.