Plain English Meaning

The engine quits burning because the fuel is spread too thinly through the air going into it. There isn't enough fuel in the mix to keep the fire going, so the flame dies.

Full Definition

A flameout in a turbine engine caused by an air-to-fuel ratio that is too high — meaning too much air for the amount of fuel being supplied — so the mixture cannot sustain combustion and the flame in the combustion chamber goes out.

Context Anchor

Encountered in turbine engine discussions, especially when learning why a flameout can occur and how fuel-air balance affects engine operation.

Derivation

Lean' in engine work means a mixture with relatively more air and less fuel — the opposite of 'rich.' A 'flameout' is exactly what it sounds like: the flame inside the combustion chamber goes out. Put together, the term names the cause and the result.