| an engine of one or more working cylinders in which the process of combustion takes place within the cylinders. |
| in·ter·nal-com·bus·tion engine (ĭn-tûr'nəl-kəm-bŭs'chən) n. An engine, such as an automotive gasoline piston engine or a diesel, in which fuel is burned within the engine proper rather than in an external furnace, as in a steam engine. |
Any engine powered by burning fuel inside it (for example, a standard automobile engine). Internal-combustion engines normally burn fossil fuels and therefore are a major source of air pollution. (See smog.)