A fuel derived from petroleum (or other oils) but heavier than gasoline/petrol. Used to power diesel engines which burn this fuel using the heat produced when air is compressed.
For a spark-ignition internal combustion engine to continue running after the electrical current to the spark plugs has been turned off. This occurs when there's enough heat in the combustion chamber to ignite the air and fuel mixture without a spark, the same way that heat and pressure cause ignition in a diesel engine.
