Nouns

(n)enginemotor that converts thermal energy to mechanical work
(n)enginesomething used to achieve a purpose“an engine of change”
(n)locomotive, engine, locomotive engine, railway locomotivea wheeled vehicle consisting of a self-propelled engine that is used to draw trains along railway tracks
(n)enginean instrument or machine that is used in warfare, such as a battering ram, catapult, artillery piece, etc.“medieval engines of war”