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