motor fuel a chemical product burnt with air in internal-combustion engines to produce mechanical energy GRM: n. Note: the term was originally reserved for products used in spark ignition engines, but is now often applied to the range of products used to fuel different types of engines (gasoline engines, diesel engines, jet engines, etc.) References: SEEpetrol SEEgas SEEgasoline SPEauto diesel oil SPEdiesel oil SPEDERV fuel SPEdiesel fuel