Plain English Meaning
The belt that connects the engine to the alternator so the engine can spin the alternator and make electricity for the airplane.
Full Definition
A flexible drive belt, usually rubber or reinforced rubber, that transfers rotational power from a pulley on the engine to the alternator, allowing the alternator to generate electrical power for the aircraft's electrical system and to charge the battery.
Context Anchor
Seen in aircraft system malfunction discussions, especially when diagnosing a low-voltage warning, alternator failure, or loss of electrical power in flight.