Plain English Meaning

The fuel in the cylinder explodes all at once instead of burning smoothly. This sudden bang puts heavy stress on engine parts and can damage the engine if it continues.

Full Definition

An uncontrolled, explosive burning of the fuel-air mixture inside a reciprocating engine cylinder. Instead of the mixture burning smoothly outward from the spark plug, it ignites spontaneously due to excessive heat and pressure, producing a sudden shock wave that hammers the piston and cylinder walls.

Context Anchor

Pilots encounter this term in piston-engine operating procedures, especially during discussions of mixture setting, high power operation, engine , , and abnormal .