Definition
A descriptive phrase identifying ignition systems in which the high voltage required to fire the spark plugs is supplied by the aircraft's battery or generator (through a coil and breaker points or an electronic ignition module), rather than by an engine-driven magneto. In a magneto system, the magneto generates its own electrical energy independently of the aircraft electrical system, so the engine continues to run even if the battery and generator fail. In a battery- or generator-powered ignition system, the engine depends on the aircraft's electrical system to keep firing.
Plain English
It means the spark for the engine comes from the airplane's battery or generator, not from a self-powered unit attached to the engine. If the battery and generator quit, the engine quits too.
Context Anchor
Seen in descriptions of aircraft engine ignition systems, especially when comparing battery-powered ignition with magneto ignition.
Derivation
Magneto comes from magnet and originally meant a machine that uses magnets to make electricity. That helps here because a magneto is not just a switch or a battery; it is a self-contained device that produces the electricity needed for ignition.
Why Pilots Care
Most certificated piston aircraft use dual magnetos specifically because they keep working with no electrical system at all. An ignition system that depends on the battery or generator removes that safety margin -- an electrical failure can stop the engine. Pilots flying aircraft with this kind of ignition need to understand the engine's dependence on the electrical system and check the relevant emergency procedures.
Intuition Check
Do not assume battery-or-generator ignition and magneto ignition fail the same way. Battery-or-generator ignition depends on the aircraft electrical system; a magneto normally makes its own ignition power.
Example Sentence 1
Some experimental aircraft use an electronic ignition powered by the battery or generator rather than a magneto, so the pilot must monitor electrical system health closely.
Example Sentence 2
During preflight the pilot confirmed the engine was battery or generator rather than a magneto.