Final answer:
The Area Minimum Altitude (AMA) is the lowest altitude used under IMC that ensures a 1,000-foot or 2,000-foot clearance above terrain and obstacles, depending on whether the area is mountainous or non-mountainous.
Step-by-step explanation:
The terminology you're referring to is known as the Area Minimum Altitude (AMA). This is the lowest altitude to be used under instrument meteorological conditions (IMC) that will ensure at least a 1,000-foot vertical clearance from terrain and obstacles in non-mountainous areas, or a 2,000-foot clearance in designated mountainous regions. This altitude is computed for safety within a specified area, considering all recorded obstacles and terrain features, and then rounded up to the nearest 100-foot increment to ensure adequate safety margins for the aircraft.