Plain English Meaning
The POH is the official handbook for a specific aircraft, written by the manufacturer. It tells the pilot how to operate that airplane safely — including normal procedures, what to do in emergencies, performance numbers, and the limits the airplane must be flown within.
Full Definition
The Pilot's Operating Handbook (POH) is the manufacturer-produced document that contains the approved operating procedures, performance data, limitations, weight and balance information, systems descriptions, and emergency procedures for a specific make, model, and serial number of aircraft. For aircraft certificated after 1975, the POH typically incorporates the (), and the pilot is required to operate the aircraft in accordance with its limitations.