Plain English Meaning
The official manual for a specific aircraft, signed off by the FAA, that tells the pilot how to operate it and what its limits are. It must be in the aircraft when it flies, and what it says is legally binding.
Full Definition
An Airplane Flight Manual that has been formally accepted by the FAA (or equivalent civil aviation authority) as the official document containing the operating limitations, procedures, performance data, and weight and balance information for a specific aircraft by serial number. The approved AFM is required to be on board the aircraft and is the legally binding source for that aircraft's operating limits.
Context Anchor
Seen when checking aircraft loading, weight-and-balance information, operating limits, and performance data before .