In the context of aviation and aerospace, "Adjacent Center Metering" does not have a widely recognized or standard definition. However, I can try to provide some insight based on possible related concepts.

In aviation, particularly in air traffic control, "metering" typically refers to the process of managing the flow of air traffic, especially during periods of high demand or when there are restrictions on the availability of airspace. This can involve spacing aircraft at specific intervals to maintain safe separation and efficient use of airspace.

The term "center" might refer to an Air Route Traffic Control Center (ARTCC), which is a facility responsible for managing air traffic within a specific region of airspace. An ARTCC is typically responsible for providing air traffic control services to aircraft operating under Instrument Flight Rules (IFR) within its area of responsibility.

Given this context, "Adjacent Center Metering" might be interpreted as a procedure or technique used to manage the flow of air traffic between adjacent air traffic control centers. This could involve coordinating the release of aircraft from one center's airspace into another, to maintain efficient use of airspace and minimize delays.

However, without more specific information or context, it's difficult to provide a more precise definition or explanation of "Adjacent Center Metering" in the context of aviation and aerospace. If you have any additional details or clarification regarding this term, I'd be happy to try and provide a more informed response.