{ or . [ After Dr. Rudolf Diesel, of Munich, the inventor. ] A type of internal-combustion engine in which the air drawn in by the suction stroke is so highly compressed that the heat generated ignites the fuel (usually a heavy oil), the fuel being automatically sprayed into the cylinder under pressure. The Diesel engine has a very high thermal efficiency. [ Webster 1913 Suppl. ]

a. Designating an internal-combustion engine of a type resembling the Diesel engine in using as fuel heavy oil which is injected in a spray just before the end of the compression stroke and is fired without electrical ignition. The fuel is sprayed into an iron box (called a hot bulb or hot pot) opening into the combustion chamber, and heated for ignition by a blast-lamp until the engine is running, when it is, ordinarily, kept red hot by the heat of combustion. [ Webster 1913 Suppl. ]