Plain English Meaning
The engine stops making power, or stops running entirely, while the aircraft is operating.
Full Definition
A condition in which an aircraft engine ceases to produce usable power, either partially or completely, due to mechanical breakdown, fuel starvation, fuel exhaustion, ignition system failure, induction problems, or other causes that interrupt normal combustion or power transfer.
Context Anchor
Seen in fuel and oil discussions, preflight planning, in-flight power checks, and emergency procedures for selecting a safe landing area.
Derivation
Engine comes from an old word meaning a device or machine. Failure comes from a word meaning to fall short or not . Together, engine failure means the power-producing machine is no longer doing its job well enough for flight.