engine in WordNet English dictionary

1. motor that converts thermal energy to mechanical work
   engine 
   
2. a wheeled vehicle consisting of a self-propelled engine that is used to draw trains along railway tracks
   locomotive  engine  locomotive engine  railway locomotive 
   
3. an instrument or machine that is used in warfare, such as a battering ram, catapult, artillery piece, etc.
   "medieval engines of war"
   engine 
   
4. something used to achieve a purpose
   "an engine of change"
   engine