A type of internal combustion engine where ignition happens when fuel is spray at high pressure into a compressed charge of air, or the relatively heavy fuel oil used in compression-ignition engines.
"A diesel engine (also known as a compression-ignition engine) is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber. This is in contrast to spark-ignition engines such as a petrol engine (gasoline engine) or gas engine (using a gaseous fuel as opposed to gasoline), which uses a spark plug to ignite an air-fuel mixture." -Wikipedia
